Are you sure that they is nothing in his cage? I mean a kind of bug. Just check it once because my friend's bearded dragon also faced the same problem, after a few days my friend came to know that the small bug was also residing in the cage along with the dragon and caused patches on the dragon...
I would like to ask that what if the veileds is not so young?
My friend had recently brought a veileds and the veileds is not young and has the habit of eating only worms?
What should be done?