Mites or just overgrooming?

Question
Hi there. I have had rats for 5 years and currently I have 7-- 3 females (2 of which are together and being introduced to the third) and 4 males (2 separate pairs which MIGHT be introduced.) Before I ask my question I just want to assure you that I have no problem taking them to the vet BUT I wanted an opinion first. Also, none of the other rats have shown the symptoms that these two are showing.

Ok, so here goes:

I have two young-ish males that I got from the local crappy petstore from the same tank so they may have been from the same litter, I really don't know. In any case, I noticed a few scattered, pin prick like scabs on one of their backs  (just the back) a while ago. Their fur was getting rougher so I assumed he was just scratching from molting (?) or being overgroomed by the other. They have long nails but are still skittish so I haven't attempted clipping them just yet. A while after, the other's fur got rougher and he got a few scabs, just on his back though! And just now I noticed that the scabs are completely gone, but their fur looks like it's thinning, just on the back.

So are they just barbering eachother? I notice a few squeaks here and there but no big injuries.

Or is this mites? None of the other rats have these symptoms.

Thanks for your time!

Answer
Generally if you're going to see scabbing from mites it'll be around the head and shoulders, not the back. Not to say its impossible, but its unlikely that its mites. If the hair is thinning, see if you can catch a peek at the hairs themselves - do they look clipped/chewed, or does it just look like a balding patch?

I've seen barbering before and its definitely a chewed off hair, not just thinning. Hairloss could be from malnutrition, skin problems, a parasite (again - unlikely to be mites, but perhaps lice?), or even just constant rubbing against a hidespot or side of the cage.