Looks like he's got some edema going on there. For some of the more supplement sensitive montane species like the merumontanus I like to rely more on proper gutloading than dusting with the various vitamins and minerals. Up his misting sessions for the next little while - the extra humidity while help with his molting too.
Good luck with him, he's a handsome fellow. Are there any ladies for him?
Cheers,
T