U.S. stock markets experienced a significant downturn, with the S&P 500, NASDAQ, and Dow Jones all closing lower. The S&P 500 dropped by 1.2%, while the NASDAQ fell by 1.75%, closing at 15,891.75. The Dow Jones also saw a decline, closing down 247.67 points or 0.65% at 37,735.57. This marked the first instance of back-to-back declines greater than 1% for the S&P 500 since last October, contributing to a two-day total drop of 2.6%, the largest in over a year. The downturn was influenced by a significant sell-off in big tech stocks, pushing the S&P 500 below the 5,100 level.