Teen clothing retailer rue21 is closing about one-third of its stores nationwide as it focuses more on its online business.The privately held company is shuttering nearly 400 stores, leaving it more than 700 stores in 48 states.The company is based in Cranberry, north of Pittsburgh. In a Facebook post , it called the decision to close the stores “difficult but necessary.” Like many brick-and-mortar retailers, it has been battling declining mall traffic amid strong competition online. According to the rue21 website, 3 stores are on the chopping block, including Centerpoint Mall, Tanger Outlets, and Riley Plaza in Holland. No closure dates were released.