Hello! It’s great to hear they are back in the house and have freedom in your sister’s room. Great!
At first I thought it might just be molting but the fact that the skin is attached sounds like it’s been pulled out – could they be fighting?
They could also be over-grooming and pulling out due to irritations by mites etc.
Also the “rash” means it could be mites or even fleas. If it is mites, people can get them on them, but they only cause a minor irritation and do not survive on humans. You will not be infested by them so you don’t have to worry about that.
If it is ring worm then yes, you can get it but don’t freak out! It is very treatable with meds from your doctor, and it will not make your hair fall out either. Rabbit can actually get ringworm from people too, so it goes both ways.
You will have to get a vet to determine what they have first. Both are relatively easily treatable. But f you let it go, it can get VERY bad. Once they are treated, you will have to wash their blankets and clean well to prevent reinfestation.
Keep us updated about what the vet says.