Profit-taking was the activity of the day for investors, resulting in the price slump.Chipotle Mexican Grill (CMG -5.24%) has been one tasty quesadilla of a stock on the exchange over the years. The fast-casual restaurant chain operator didn't have a good session on the market Thursday, however. Its shares fell more than 5% in value, which wasn't unusual given what happened the previous day.Stock-split indigestionChipotle investors started Wednesday with a much higher number of shares than they held previou ...