Sellers got out the big knives Thursday as the indexes lost chunks and leading stocks were slashed. The Nasdaq dropped for a fourth session in a row, lopping off 1.6%. The S&P 500 sliced off 1%, while the small-cap Russell 2000 axed 2.2%. The IBD 50 carved off 2%. Volume rose across the board. The action slapped the Nasdaq and S&P 500 with distribution days, even as the March 25 distribution day fell off the count.