NEW YORK (TheStreet) -- The SPDR S&P Biotech ETF (XBI - Get Report) has survived a tough three months, dropping to $60 recently after it had traded at $90 in July. The On-Balance-Volume (OBV) line suggests that people piled into biotechs this spring, late in the advance and right before the decline to $60.

In this chart of XBI, above, notice the sharp rise in the OBV line in May, June and July. As prices peaked and declined, the OBV moved lower, telling us that volume was heavier--read selling--on days when XBI closed lower.

This short-term candlestick chart, above, shows that recently XBI has been making what are called "lower shadows." Candlesticks show the relationship between the open and the close of trading as a "real body."

The highs and lows of the session are not as important and are called "shadows," which can tell us if the highs or lows were rejected. Notice how in this chart above, the XBI has finished the day with lower shadows, meaning that prices did not close at or near the low of the day. This is a small positive.

Juno Therapeutics  (JUNO) seems to be a bigger weighting in the XBI and so far has led off the bottom with a rally starting at the end of August/early September. We'll be watching to see if JUNO's leadership spreads to other names in this space.