I have a white rabbit and lately I've noticed her fur turning yellow, her paws, around her but, and one side of cheek. I know I shouldn't give her a bath, but washcloths arnt taking it off nether is viniger. How do I have the yellow stain appear less often? I've read that their fur outgrows and then it's white again, but why does it turn yellow, is it pee? She uses a litter box. Has like pellet litter and hay on top.