WASHINGTON – The U.S. government began enforcing restrictions Thursday on flavored electronic cigarettes aimed at curbing underage vaping. But some teenagers may be one step ahead of the rules. Parents, researchers and students warn that some young people already have moved on to a newer kind of vape that isn’t covered by the flavor ban. These disposable e-cigarettes are sold under brands such as Puff Bar, Stig and Fogg in flavors such as pink lemonade, blueberry ice and tropical mango. The Food and Drug Administration’s crackdown narrowly targets reusable vaping devices such as Juul, the blockbuster brand that helped trigger the teen vaping craze in the U.S.