I have 4 female mice from a show breeder, I've had them about 6 weeks and they are constantly pooping and peeing in their food bowl! When they had a wire tank topper, I tried securing it on the top mesh level - didn't help. Tried higher and lower edged bowls, didn't help. Moved away from and closer to their nest -- they still do it! Has anyone else had this problem?? I mean they actually start using it as a toilet once the first one of them goes in there. What do I do?!