Hair Loss Question

I have three female rats, all living together. The alpha lady rat is losing quite a bit of hair, but it doesn't seem to be any of the usual culprits.
The hair loss is on a back leg and the surrounding area, and has recently started happening on her front leg. The skin underneath the hair loss is completely normal though. No signs of dryness or flaking.
The other rat is completely normal (the third is a hairless) and this has been going on long enough that I'd expect it to have spread if it were contagious (it never looked contagious, which is why I didn't separate the one losing hair).

Any ideas what could be going on?

It really sounds like barbering to me. It can happen between cagemates and is not life threatening, just looks strange. From where you say the hair loss is I would guess that the rat is actually doing it to herself. If can occur if the animal is stressed, so look for opportunities to decrease stressors. However, some rats will make a habit of it anyways. Please keep us updates on how she does.

Thanks for the response!
That's whatI kind of thought it might be. She's the alpha lady of the cage, so I can definitely tell her stress level goes up if she feels like she has to make sure the other two aren't acting silly.

I've seen it in mice before, but it's always been kind of a situation where I adopted one with serious OCD, so it'd look BAD.

Yeah, definitely barbering.

After dealing with an abscess under the hind leg of one of the other rats, I'm kind of relieved this is just barbering. I'm going to try adding some new toys and hammocks and see if that'll distract everyone.