Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Last night, after Apple reported disappointing earnings that sent the stock plunging in after-hours trading, it appeared that the stock market might be in for yet another losing day today. But even though major stock market benchmarks managed to post solid gains, that didn't prevent some major losses in other key stocks, including Rent-A-Center (NASDAQ: RCII), Chefs' Warehouse (NASDAQ: CHEF), and Seagate Technology (NASDAQ: STX).

Rent-A-Center plunged 22% after the provider of rental and rent-to-own furnishings reported that net income fell by 72% in its fourth quarter. A 1.1% drop in same-store sales held back overall revenue growth to just 2%, and cautionary guidance for 2014 pointed to the ongoing problems for Rent-A-Center's cash-strapped customer base. The results throw cold water on the idea that the U.S. economic recovery has been felt equally across those of all income groups, as CEO Mark Speese said that its customers are still "under severe economic pressure" that could weigh on results into the future.

Chefs' Warehouse fell 14% after giving an earnings warning after the market closed yesterday afternoon. The specialty-food distributor said that it now expects revenue of between $670 million and $673 million for the full 2013 fiscal year, with net income of $16.5 million to $16.7 million and adjusted earnings per share of $0.80 to $0.81. Chefs' Warehouse also disclosed an accounting issue related to alleged employee malfeasance, but it also blamed adverse weather and high costs that pressured profit margins as causes for the poor guidance. The company also got downgraded by BB&T Capital Markets following the downbeat warning.

Seagate Technology dropped 11%, in the aftermath of its own poor earnings report. Seagate missed earnings estimates for the quarter by $0.06 per share, and its revenue guidance for the current quarter led investors to believe that its sequential sales would fall even more than expected. Despite a smart strategy that involves trying to evolve past its hard-disk drive prowess to play a bigger role in the enterprise solid-state drive market, Seagate hasn't been able to capitalize on that opportunity as much as it had hoped. Still, with relatively cheap valuations, Seagate could regain today's losses in the near future if it can execute better on the enterprise side of the business and take full advantage of the potential of cloud computing.

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Dan Caplinger owns shares of Apple. You can follow him on Twitter: @DanCaplinger. The Motley Fool recommends and owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.