A steep drop-off in grocery store operators helped pull stock indexes slightly lower after a day of up-and-down trading, the AP reports. Kroger dropped 8.1% Thursday after Whole Foods Market said its deal to be acquired by Amazon would close on Monday and that the store would begin cutting prices immediately. Costco lost 5%. Food companies slumped after the makers of Spam and Folgers coffee reported weak results. Hormel lost 5.4% and J.M. Smucker fell 9.5%. The Standard & Poor's 500 index lost 5 points, or 0.2%, to 2,438. The Dow Jones industrial average gave up 28 points, or 0.1%, to 21,783. The Nasdaq fell 7 points, or 0.2%, to 6,271. Small-company stocks rose. The Russell 2000 index climbed 4 points, or 0.3%, to 1,373. (More stock market stories.)