The recent rebound in U.S. markets has been spectacular for anyone who owns stocks right now. In the last few weeks, the big S&P 500 index has swung from 52-week lows to back within grabbing distance of breakeven for 2016.

No doubt, investors are breathing a little easier than they were a month ago when the selloff was in full swing.

But it's a mistake to think that you can take your finger off the trigger in March -- U.S. markets may be rebounding, but those stats ignore the fact that one in five S&P components is still down 10% or more as of this writing. In short, stocks may be working again, but a big pocket of the broad market still looks "toxic" for your portfolio. Avoiding those names could be the best thing you do for your portfolio this year…

To spot the next round of red flags, we're turning to the charts for a technical look at five big-name stocks that could be turning toxic here. For the unfamiliar, technical analysis is a way for investors to quantify qualitative factors, such as investor psychology, based on a stock's price action and trends. Once the domain of cloistered trading teams on Wall Street, technicals can help top traders make consistently profitable trades and can aid fundamental investors in better entry and exit points.

Just so we're clear, the companies I'm talking about today are hardly junk. By that, I mean they're not next up in line at bankruptcy court – and many of them have very strong businesses. But that's frankly irrelevant to what happens to their stocks; from a technical analysis standpoint, sellers are shoving around these toxic stocks right now. For that reason, fundamental investors need to decide how long they're willing to take the pain if they want to hold onto these firms in the weeks and months ahead. And for investors looking to buy one of these positions, it makes sense to wait for more favorable technical conditions (and a lower share price) before piling in.

So without further ado, let's take a look at five "toxic stocks" to sell.

BP 

Up first is integrated oil and gas giant BP  (BP - Get Report) . By and large, energy stocks have been rebounding hard in the last few weeks -- the big Energy Select Sector SPDR ETF  (XLE - Get Report)  is actually above breakeven on the year, for instance. But BP hasn't been participating in the upside. Instead, shares are holding onto their red ink right now; and they could be pointed even lower thanks to a bearish technical setup that's been forming in shares.

BP has been forming a descending triangle pattern, a bearish continuation setup that's formed by horizontal support down below shares (at $28 in BP's case), and downtrending resistance to the upside. Basically, as shares of BP ricochet in between those two technical price levels, this stock has been getting squeezed closer and closer to a breakout through our $28 price floor. If that $28 level gets violated, look out below.

Relative strength, which measures BP's price performance versus the broad market, is an extra red flag to watch here. Our relative strength line is still holding onto its downtrend from the beginning of last summer, which tells us that this stock is still underperforming the rest of the market in the long-term. If $28 gets violated, look out below.

Mean Johnson Nutrition 

We're seeing the exact same setup in shares of $14 billion nutrition company Mead Johnson Nutrition (MJN) . Like BP, Mead Johnson is currently forming a descending triangle pattern. Support has been in a range in Mead Johnson, coming in between $67.50 and $70 per share. If the lower bound of that range, $67.50, gets busted, then look out below.

Why all of the significance at that $67.50 level? It all comes down to buyers and sellers. Price patterns, like this descending triangle in Mead Johnson, are a good quick way to identify what's going on in the price action, but they're not the actual reason a stock is tradable. Instead, the "why" comes down to basic supply and demand for shares of the stock itself.

The support range in Mead Johnson is a place where there has been an excess of demand for shares; in other words, it's a spot where buyers have previously been more eager to step in and buy shares than sellers have been to take gains. That's what makes a breakdown below $67.50 so significant -- the move would mean that sellers are finally strong enough to absorb all of the excess demand at that price level. Keep a close eye on that $67.50 level as we head deeper into March.

Erie Indemnity 

Mid-cap insurance stock Erie Indemnity (ERIE - Get Report)  has been enjoying a strong run in the last six months, up nearly 20% at the same time that the S&P 500 has barely peeked its head above breakeven. But Erie's rally is starting to show some cracks in 2016. Here's why it makes sense for shareholders to start taking some gains on this $5 billion financial firm.

Erie is currently forming a double top, a bearish reversal that looks just like it sounds. The double top is formed by a pair of swing highs that peak around the same level -- they're separated by a trough that marks the breakdown level for Erie. That price floor comes in at $91 support, and if it gets violated, Erie could have a prolonged fall ahead of it.

Momentum, measured by 14-day RSI in Erie, adds another red flag for shareholders to be aware of here. Our momentum gauge made a pair of lower highs at the same time that Erie's price action was testing the $100 resistance level for the second time. That's a bearish divergence that signals buying pressure waning in 2016. So, if $91 support gets broken, Erie becomes a sell.

Tiffany 

It's been a tough year to own luxury jeweler Tiffany (TIF - Get Report) . In the last 12 months, share of Tiffany have shed 22% of their market value, selling off about four times as badly as the broad market over that stretch. Tiffany has shown some glimmers of hope more recently, though. In the last month, this stock has rebounded 8.4%. But that recent rally should be viewed with suspicion.

Since last summer, Tiffany's selloff has been corralled neatly in a well defined downtrending channel. That pair of parallel trendlines that has marked the high-probability range for shares to stay within -- and they have, reversing off of resistance on the last five tests. Now, as shares come up to test resistance for a sixth time, it makes sense to sell the next bounce lower in shares of Tiffany.

Waiting for that bounce lower before clicking "sell" is a critical part of risk management for two big reasons: It's the spot where prices are the highest within the channel, and alternatively it's the spot where you'll get the first indication that the downtrend is ending. Remember, all trend lines do eventually break, but by actually waiting for the bounce to happen first, you're confirming that sellers are still in control before you unload shares of Tiffany.

National Retail Properties

Last up on our list of potentially toxic trades is mid-cap REIT National Retail Properties  (NNN - Get Report) . National Retail Properties has actually been a serious outperformer in the last half-year; over that stretch, shares have rallied almost 30% while the broad market was floundering. But it might be about time to start thinking about taking some gains off the table in this commercial landlord.

That's because National Retail Properties is currently forming a rounding top, another technical pattern that looks just like it sounds. National Retail Properties' pattern indicates a gradual shift in control of shares from buyers to sellers -- and it triggers if support at $44 gets violated. Shares are testing that key price floor this week.

National Retail Properties' price setup is a near-term pattern. That means it's most likely a correction, not a crash. But it also means that shares are likely to retrace 10% to trendline support at $40 before they encounter any semblance of a price floor again. That's good reason to keep a close eye on this pattern in March. If $44 gets busted, it opens up double-digit downside risk.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.