The energy sector was one of the few that still gained, as rising oil prices helped lift shares of major oil producers. Major U.S. equities indexes lost ground Tuesday afternoon, after Federal Reserve Chair Jerome Powell said the central bank faces a "challenging situation" ahead. Vistra (VST) shares also fell following a downgrade from Jefferies, which argued the power company’s stock price is too high. Meanwhile, the energy sector was one of the few that still gained, as rising oil prices helped lift shares of major oil producers like Halliburton (HAL), Baker Hughes (BKR), and Diamondback Energy (FANG). The U.S. dollar was up on the euro and yen, but lost ground to the pound.