Stocks showed weak action Thursday for a second day in a row, as the Nasdaq lost a key support line. The Nasdaq fell 0.7%, driven partly by an almost 2% drop in Apple (AAPL). The former leader accounts for about 9% of the Nasdaq's weighting. The S&P 500 and the NYSE composite retreated 0.6% and 0.5%, respectively. The IBD 50, a proxy for leading stocks, skidded 1%. Volume declined on the NYSE and rose on the Nasdaq. The action on the Nasdaq