Tuesday brought further losses to the stock market, with somewhat steeper and broader-based declines than investors saw on Monday. Even though most major-market benchmarks lost only about half a percent, the brunt of the selling pressure seemed to center on some of the best-performing stocks in the recent past. Among the stocks that performed the worst today were Plug Power (NASDAQ:PLUG), as well as Bridgepoint Education (NYSE:BPI) and Nuverra Environmental Solutions (OTC:NESC).

Plug Power plunged more than 40% after becoming the latest target of Citron Research, which penned a report that questioned the fuel-cell systems company's business model and suggested that the stock's fair value was just $0.50 per share. The report described a long history of statements from CEO Andy Marsh relating to unit sales that turned out to be overly ambitious, and pointed to large and in hindsight ill-timed offerings of shares and convertible securities at very low prices. Ballard Power Systems (NASDAQ:BLDP), which has a closer relationship with Plug Power, also fell hard on the news, losing more than a quarter of its value. FuelCell Energy (NASDAQ:FCEL) was also a victim of the dour view of the industry, falling 17% despite initially rising after reporting earnings last night that included a 22% jump in sales.

Bridgepoint dropped 16% as the for-profit educational company fell well short of investor expectations in its latest earnings report. Revenue fell by almost 22% on an identical percentage drop in total student enrollment at Bridgepoint's Ashland University and University of the Rockies. Despite an encouraging increase of about 10% in new-student enrollments, the company's loss defied expectations of a small profit for the company. Other for-profit educational institutions fell in sympathy, and it's clear that the challenges for the industry are far from over even though hopes for a turnaround have gotten more frequently lately.

Nuverra slid 15% after the company's earnings release last night. Revenue for the unconventional oil-and-gas environmental services specialist fell by about 5% sequentially from the third quarter, as tough weather hurt the company. In addition to earnings, Nuverra announced it would sell its Thermo Fluids division to VeroLube for $175 million, with all but $10 million coming in cash. Investors might not have been thrilled with the sale, simply because the price represents a $70 million loss compared to what Nuverra paid for the business just two years ago. Yet Nuverra's sale is part of its broader strategy to focus on its shale-play environmental solutions business, and many believe that a more focused approach should bring better long-term results for the company. With Nuverra also having resolved some other old issues, including settlement of class action litigation and a transition in the board of directors, the stock could rebound eventually from today's losses.