Friday was a down day on Wall Street, but losses were generally small, and the market closed well above its lowest levels of the session. Initially, investors seemed concerned about further trade tensions between the U.S. and China, but upon further reflection, they appeared to draw comfort from considerable fundamental strength from key sectors of the industrial economy. Even with the overall market recovering from earlier weakness, some stocks still posted substantial declines. Whiting Petroleum (NYSE:WLL), Global Blood Therapeutics (NASDAQ:GBT), and First Solar (NASDAQ:FSLR) were among the worst performers on the day. Here's why they did so poorly.

Whiting falls with oil

Shares of Whiting Petroleum dropped more than 9% on a bad day for the energy markets generally. Crude oil fell nearly $2 per barrel, dropping below the key $65-per-barrel level as production levels within the U.S. have continued to climb. Many investors had hoped that producers like Whiting would be able to maintain enough discipline even with crude prices having risen throughout much of early 2018. But even if exploration and production companies aren't in a hurry to spend a lot of extra money on capital investments, it's still hard for them not to take measures to boost production when pricing conditions become more favorable. Given potential action from overseas producers as well, Whiting will have to navigate rapid changes in energy market conditions for the rest of this year and beyond.

Man in hard hat and safety glasses with handheld monitoring device in front of a pumping oil well.

Image source: Whiting Petroleum.

Global Blood disappoints

Global Blood Therapeutics stock plunged 15% after the biotech specializing in blood disorders reported on one of its phase 2 studies of sickle cell disease treatment voxelotor. The data showed encouraging results, according to CEO Ted Love, and Global Blood seems optimistic that the treatment could end up helping both adolescent and adult patients fighting the disease. Yet investors seemed to want more definitive data showing the advantages of voxelotor. They might get their wish when Global Blood releases data from a phase 3 study of it in the near future, but for now, shareholders weren't eager to hold onto their positions.

First Solar cools off

Finally, shares of First Solar dropped 5%. The solar giant has lost a quarter of its value just since the beginning of June following news that China would reduce the incentives it offers for solar projects for the remainder of 2018, cutting off a huge source of demand for the industry overall. As trade tensions between the U.S. and China escalate, it's also possible that First Solar could find itself at the center of a key dispute, given the importance of the solar industry to both countries. Today's decline suggests further nervousness about what could be the next shoe to drop for the solar industry, and First Solar doesn't seem to be able to escape potential negative impacts despite its prominence and leadership role in solar energy.