User blog comment:Leon Jung/I wonder if the Winx could use their old power?/@comment-10921179-20140423073044/@comment-27111026-20140426100644

The Charmix and Gloomix are not actually "new power", as they don't give the Winx or Trix new outfits/appearance, yet just appear as accessories; they are in fact just power boost. And because so, when you're out of them, you can't use them ever again. They're not fuel so when you're out of fuel you can re-fuel them again.