Stocks tumble on weak earnings and regional bank concerns.

Several big stocks, including First Republic Bank, Enphase Energy, and Activision Blizzard, recorded losses in Wednesday's session due to weak quarterly results and poor guidance. First Republic Bank shares tumbled 39.3% after announcing a decline in deposits and revenue for Q1, while Enphase Energy shares declined 23.9% after reporting worse-than-expected Q1 sales and weak Q2 guidance. Activision Blizzard fell 10.8% after the UK's CMA reportedly prevented Microsoft's proposed purchase of the company.