Fighting/playing female rats

Question
hello, I have 4 Dumbo rats all female from a pet shop all from the same parents.I have had rats before this but only 2 at a time.
They are in a very big gage and have lots to do, but they fight alot, is this anything to worry about? I thought that maybe it was a territorial thing? But as one of them has some fur missing under her neck,I was a little worried. They are very friendly indeed, and I have even managed to bath them. :) thank you

Answer
It may be a territory thing. Do they range in age at all? Sometimes as they hit puberty they'll start squabbling. Be sure they've always got food on hand, and have multiple sleeping areas. If the fighting gets bad enough to draw blood, you'll need to separate.