Spots on Blue Tang... possible disease???

[bimmer88]

So my 5" blue tang which I've had since it was the size of a quarter has recently(last 3-4 months) developing some spots on it's face... Just looks like spots where it loss color... I figured this is probably what happens when they get bigger since I've seen other blue tangs in fish stores that seem to be like this before... the other day I went to Steinhart Aquarium(the type that doesn't sell fish.. just display) and I saw a number of larger blue tangs that didn't have this problem... Can this be some kind of disease my fish has??? Other than these spots, his behavior hasn't changed... seems perfectly healthy... Attached is a picture... in the picture they look like black spots but in real life they are not black... just looks spots where color disappeared.... Any idea if this is some type of ailment??? He doesn't seem effected at all... just runs the tank like he's the boss as usual.

 

[Mrscribbled]

This is common in this species, not sure why. Nothing to be worried about.