Stocks generally finished February on a strong note and, even though the market finished off its highs of the day, the S&P 500 again hit new all-time record highs and lifted most individual stocks along with it. But bad news still hit a few companies, and shareholders of Clean Energy Fuels (NASDAQ:CLNE), Medivation (NASDAQ:MDVN), and NII Holdings (OTC:NIHDQ) all suffered big declines today that even the cheerful mood on Wall Street wasn't enough to overcome.

Clean Energy Fuels fell 14% after the natural-gas refueling station and infrastructure company's fourth-quarter results failed to meet investors' ambitious growth hopes. Delivery volume rose 13% after adjusting for continuing operations, but the company's adjusted net loss widened from year-ago levels, and revenue fell short of overall expectations. In the long run, Clean Energy Fuels faces a large number of challenges, including rising competition and soaring natural-gas prices, that could lead some potential customers to delay or cancel plans to convert from oil-based fuels to natural gas.

Medivation dropped 15% as the maker of biopharmaceutical cancer treatment Xtandi gave guidance for the fiscal 2014 year that fell short of what investors had hoped to see. Medivation posted a surprising profit for the quarter on revenue growth of 160% compared to the year-ago quarter. But the company's 2014 forecast suggested that Medivation doesn't expect that pace of sales growth to continue, with guidance for revenue of $500 million to $535 million falling short of expectations. Of greater concern is that, if growth in Xtandi sales slows down even further, the prostate-cancer treatment could end up not becoming the blockbuster drug that so many foresaw it becoming. That concern is one reason why analysts at Jefferies downgraded Medivation stock today.

NII Holdings plunged 55% after its earnings report raised questions about how long the mobile-phone service provider will be able to keep operating. The company lost nearly a quarter of a million customers in the fourth quarter, and net losses of nearly three-quarters of a billion dollars for the quarter only accentuated the balance-sheet stress that $3.4 billion in debt, net of cash and investments, is having on the company. With NII Holdings warning that it might have to take measures to raise capital in order to avoid a liquidity crunch as soon as next year, even bond investors aren't convinced that the company will be able to make good on its obligations and avoid default.