Stocks finished narrowly lower on Tuesday, as investors seemed content with the impressive gains they've scored so far this month after a terrible January. Yet even though broad market benchmarks fell only a fraction of a percent, much larger losses hit shares of SINA (NASDAQ:SINA), VIVUS (NASDAQ:VVUS), and Tenet Healthcare (NYSE:THC) today due to company-specific news affecting their respective businesses.

SINA fell 9% after the company's quarterly earnings report prompted pessimism from investors and a price-target drop from analysts at Maxim Group. Sales grew by 43%, with impressive gains in both advertising and non-advertising revenue from SINA's key Weibo microblogging service. Yet growth in the number of average daily users of the Weibo service climbed by just over 4% from the third quarter, indicating slowing interest and increased competition from rival services. With no comments on speculation that SINA might make a public offering of shares of Weibo directly, investors didn't hear what they'd wanted the company to say to them today.

VIVUS dropped 13% despite seeing its losses narrow by 70% from year-ago levels, far exceeding the hopes of most investors. Yet another disappointing quarter of sales from the company's key Qsymia anti-obesity drug offset any enthusiasm from licensing deals for its erectile-dysfunction treatment. Moreover, the specter of potential new competition from Orexigen's (NASDAQ: OREX) Contrave later this year could pose an even bigger threat to VIVUS even if it can overcome its immediate need to drive sales higher.

Tenet declined 9% after reporting its own losses last night. Even after successfully completing its acquisition of Vanguard Health Systems, the hospital operator's guidance for 2014 disappointed investors, with EBITDA projections coming in 3% to 8% below what most investors had expected to see from Tenet. Even news yesterday that Tenet would expand a deal with Aetna (NYSE: AET) to accept insurance and participate in state-exchange plans in seven markets, further uncertainties about the way that health-care reform efforts will play out still exist. Many investors believe the risk-reward equation for Tenet doesn't look favorable enough to justify maintaining holdings in the stock.