The charts for nuclear power plays Vistra and Constellation Energy suffered notable setbacks this week, leading the losses on the S&P 500 on Wednesday. Vistra recently leapt past Nvidia, taking the mantle of "new king" as the S&P 500's top gaining stock this year. Vistra advanced 1% to 125.41 and CEG edged up 0.8% to 264.28 Thursday during market action.