Major benchmarks gained ground on Monday, finishing the third quarter on an optimistic note. Investors have gotten whipsawed on various news items coming out of Washington, and today's more positive tone in trade relations with China improved market sentiment. Yet there were still some big challenges that some companies faced, pulling their share prices down. Cal-Maine Foods (NASDAQ:CALM), G1 Therapeutics (NASDAQ:GTHX), and Teekay LNG Partners (NYSE:TGP) were among the worst performers. Here's why they did so poorly.

Cal-Maine lays too many eggs

Shares of Cal-Maine Foods fell 12% after the egg producer reported its fiscal first-quarter results. The company said revenue was down 29% and that it reversed a year-earlier profit with a significant loss. A glut of eggs in the overall industry reduced prices by more than 40% in the Southeastern U.S. compared to where they were 12 months ago, and a slight gain in sales volume wasn't nearly enough to make up for that downward pressure. Specialty egg products will continue to play a key role in driving Cal-Maine's growth because they're less sensitive to commodity pricing pressures, but investors will have to deal with getting no dividend under the company's variable-dividend policy until Cal-Maine becomes profitable again.

Large batch of brown eggs in a production facility.

Image source: Getty Images.

G1 releases trial data

G1 Therapeutics saw its stock plunge 33% following its release of trial data over the weekend. Preliminary results from its phase 1/2a study of candidate breast cancer treatment G1T48 showed that the drug was well tolerated even at escalated dose levels, but clinical benefit rates were relatively low at 16%. Meanwhile, a phase 2 study of trilaciclib to treat triple-negative breast cancer showed a significant increase in overall survival as part of chemotherapy compared to using chemotherapy alone. G1 hopes to conduct further trials of the two therapies, but investors still haven't seen everything they were looking for from the studies.

Teekay deals with international intrigue

Finally, shares of Teekay LNG Partners dropped 10%. The liquefied natural gas tanker company faces new sanctions because of its joint venture with Chinese shipping giant COSCO. In its defense, Teekay said that it hasn't traded and won't trade with Iran in defiance of any trading sanctions. However, the sanctions are a big blow to the company, which enjoys a competitive advantage in being able to navigate in the Arctic to reach LNG terminals along Russia's northern coast. As trade issues get more complex, more companies like Teekay could find themselves at the center of contentious disputes among global players in key industries.