On Thursday, stock market investors initially panicked on news from Europe that suggested that a potential new financial crisis might arise involving the Portuguese banking system. Throughout the day, though, U.S. markets steadily recovered. While the market still finished down, declines were generally in the range of half a percent or less. Still, some high-profile investors are starting to look for a possible correction, and for Potbelly (PBPB), Tile Shop Holdings (TTSH 1.40%), and Fortuna Silver Mines (FSM 1.06%), the overall market's partial recovery was too little to save them from large drops today.

Potbelly plummeted 25% as the sandwich-store chain cut its guidance for the second quarter, saying that same-store sales fell 1.6%, and that net income would fall by almost 30% from year-ago levels. Moreover, Potbelly cut its full-year guidance, as well, with earnings per share likely to fall short of last year's levels by nearly half, and full-year comps coming in flat, at best. After having wooed IPO investors with the promise of being another high-growth fast-casual chain, Potbelly has started having growing pains, and unless the company can start earning better profits from its sales, the stock could potentially have even further to fall.

Tile Shop Holdings fell 9% in sympathy with other stocks in the home-improvement space, with one of its major flooring peers falling even more dramatically today after reporting weak traffic figures, and poor same-store sales for the second quarter. Even as the housing market has recovered, investors now fear that home renovation and remodeling activity might be lagging behind the home-price gains we've seen during the past year. Unless Tile Shop Holdings can differentiate itself from its competitors, it's likely to suffer some of the same headwinds that have hit the whole industry in recent months.

Fortuna Silver Mines dropped 10% despite precious metals generally having a strong day. Fortuna gave its preliminary production report for the second quarter, saying that it produced 1.6 million ounces of silver, and slightly more than 8,500 ounces of gold during the quarter, bringing its midyear production totals to around 52% to 53% of Fortuna's previous full-year guidance. Yet, as solid as these results were, they weren't enough to sustain Fortuna's upward momentum, with the stock having risen more than 70% in less than two months before today's drop. Fortuna Silver Mines has plenty of growth potential, but high valuations could prevent new shareholders from participating in that growth as much as those who bought at recent lows.