From the sounds of it, that's normal. Zebra danios have a set of barbels, so they are actually little whiskers protruding from their face. http/nis.gsmfc.org/photo/Brachydanio_rerio.jpg
All of my danio's have small barbels, just most of the time they seem to keep them close to the sides of their mouth/face so they aren't really visible.
Every so often one will have it's barbels out/down so they can be seen - doesn't seem to be any specific times that it happens though.