I have 3 rats, all females. I just got my most recent rat about a month ago, and one of my girls just will not take to her. She'll bite to draw blood, attack, pounce, anything really. I have to spray her with the spray bottle to make her stop. The new rat has trouble fighting back, and usually just lays there crying. They're fine on nuetral ground, but the minute they're in the free range area, it's over, as well as the cage, no matter how much I clean it. Also, the agressive rat doesn't touch the other old rat, mostly because she can fight back just as easily. What am I supposed to do?