Forever 21’s US operator on Sunday filed for bankruptcy for the second time in six years and said it would wind down operations in the country, hurt by mounting online competition in the fast-fashion sector and weak mall traffic. The company blamed the situation on higher costs and foreign companies taking advantage of duty-free treatment of low-cost packages from China to undermine its pricing power. “We’ve been unable to find a sustainable path forward, given competition from foreign fast-fashion companies, which have been able to take advantage of the de minimis exemption to undercut our brand on pricing and margin,”