Stocks traded mostly higher at midday on Tuesday, with the major averages building on early gains. The Nasdaq traded above its record high. Shares of Chipotle (CMG) - Get Chipotle Mexican Grill, Inc. Report moved higher after it reported same-store sales improved in the fourth quarter, as it continues to recover from a food safety scandal last year. The company also authorized a 100 million share buyback. Canadian firm Gildan Activewear (GIL) - Get Gildan Activewear Inc. Report has won the auction to acquire the American Apparel brand and some assets. The company paid $88 million in cash for those assets, but it won't be buying any retail stores. Biotech company Sarepta Therapeutics (SRPT) - Get Sarepta Therapeutics, Inc. Report advanced after the company released sales numbers for its new drug to treat a type of muscular dystrophy. The results were higher than analyst expectations.