Stocks turned mixed early Tuesday afternoon as improved retail sales and inflation data tempered concerns about a brewing fight over raising the nation's debt ceiling. The Nasdaq was down 0.3% while the S&P 500 and the Dow Jones industrial average were down a fraction after paring earlier losses. Volume was down 2% on the Nasdaq and up 2% on the NYSE compared with the same time Monday. Apple (AAPL) fell for a second day, hitting an 11-month low,