Stocks worsened and were at session lows Monday afternoon. The Dow Jones industrial average and the S&P 500 joined the Nasdaq in negative territory. The Nasdaq was off by 0.6% after rising as much as 0.5%. It turned tail after hitting resistance at its 50-day moving average. The S&P 500 fell 0.5% and the Dow lost 0.4%. Volume was tracking higher on both major exchanges in the stock market today.