Stocks tumbled further south Wednesday, dragging down even some stocks that reported strong quarterly results. The Nasdaq plunged 2.7%, the NYSE composite 2.4% and the S&P 500 2%. The Dow slid 1.2%. Volume was up across the board. The IBD 100 plunged 3.4% as many leaders of the recent market uptrend sold off and more pierced their 50-day moving averages. Every major index except the Dow closed below its 50-day line for the first time since