Stocks slumped on Thursday, leaving the Dow with only small gains for the month. Markets were under pressure following the latest signs of an economy merely limping along and as investors digested key earnings reports. Biotech stocks were the worst performers on the Nasdaq, led by Celgene (CELG) which missed quarterly revenue estimates. Chinese search engine Baidu (BIDU) was also lagging the Nasdaq after reporting its slowest quarterly sales growth in nearly 7 years. Apple (AAPL) weighed on the Dow and led losses among the tech sector. Viacom (VIAB) slid after swinging to a net loss in its second quarter.