Stocks retreated Thursday, with the Nasdaq falling the most, driven by losses in the index's two most heavily weighted components. The Nasdaq slashed 1%, while the S&P 500 and the NYSE composite held their losses to 0.2% and less than 0.1%, respectively. The IBD 50 dropped 2.4%. Volume rose across the board. The divergence between the indexes was partly due to the action of two stocks. Apple (AAPL), which makes up 10.8% of the Nasdaq's weighting