After being one of the stock market's top titans, Ulta Beauty Inc.  (ULTA) - Get Report has shown some cracks in its armor. The stock has tumbled roughly 15% over the past month, erasing all of its year-to-date gains and now down about 4% in 2017.

On Monday, shares fell another 1.6% after analysts at Oppenheimer downgraded the stock to market perform from outperform. They also lowered their price target to $270 from $330, still implying about 10% upside from current levels.

What was the catalyst for the downgrade? Part of it was the mass market slowdown in the U.S. Most investors weren't really aware of this until the L'Oreal conference call, TheStreet's founder Jim Cramer, who also manages the Action Alerts PLUS charitable trust portfolio, said on CNBC's "Mad Dash" segment.

When listening to the call, CEO Jean Paul Agon, who's lead the company since 2006, said there's been pressure in department stores and in the mass-market business. Given that Ulta is L'Oreal's No. 1 partner, that's likely to mean bad news for Ulta.

"I was very surprised," Cramer said of the CEO's comments. They're not blaming Ulta, they are very much on board with them. But the decline is unexpected and mostly without much explanation.

"It was a really interesting and very downbeat conference call," Cramer reasoned, noting that Estee Lauder (EL) - Get Report is not seeing the same weakness in the U.S. market. However, he did point out that Estee Lauder is not in the mass market business and is more high end, thus potentially protecting it from any possible short-term slowdowns.

While Ulta stock is down 6% over the past 12 months, it's still up 47% over the past two years and 137% over the past three.

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At the time of publication, Jim Cramer's Action Alerts PLUS had no position in any companies mentioned.