Stocks rolled out to a soft start Tuesday, with homebuilders and retailers stepping out to early gains. The Nasdaq dropped 0.2%. The S&P 500 and the Dow Jones industrial average trimmed 0.1% apiece. Volume was mixed, a shade lower on the Nasdaq and up 6% on the NYSE compared with the same time Monday. The stock market today opened feeling some mild downward pressure from overseas, where China’s mainland markets dropped hard on Tuesday.