scratching & bald patch

One of my girls seems to be scratching a lot at the minute. I have checked and can't see any mites or lice on her or any of the other girls or boys (all share an srs). She also has a small bald patch, like a thin line about 5mm long and 1mm wide, give or take. It's on her lower tummy. There's no wound and she doesn't seem bothered by it. None of the other girls or boys seem to be scratching and none others have bald patches bar Monk who's a oldie rex.

What could be causing the scratching?
And what's her baldy line all about?

Can be all sorts of things causing this - my guess could be that the bald bit is barbering if she's at all stressed - and it can be the slightest and least obvious things causing any stress. She could have a mite flare up - you can't see mites - they're microscopic. I would treat for mites and see if she improves.

xx

Thanks, i'm gonna get some beaphar tomorrow and change bedding again in case it is mites and they came from the carefresh.
She doesn't seem at all stressed. She was out running about as usual, super licky and cuddly with me. She seems super happy.