Big-box retailers retreated Thursday in the stock market today, on good, but not good enough, earnings from Sears Holdings (SHLD) and limp guidance from midtier chain Kohl's (KSS). Those followed the disastrous numbers from J.C. Penney (JCP) Wednesday night. Kohl's fell 0.3% in early afternoon trading. Sears rose early, but reversed and was down 5.3% intraday. Penney, which is struggling to reboot its business, tumbled 14.2%. All three cater to