My rats get along pretty well, but sometimes on a rare occasion, they'll start nipping at each other, especially when they're in their house. I'm not sure if it's attempting to claim dominance, but they'll both chase after each other for no reason, but then they'll stop and then fall asleep right next to each other as if nothing happened. When I give one rat a treat and give the other one the same type of treat, one rat will forget that I gave them one and they'll fight over the treat when both have one each. Is this play fighting or serious fighting? They like to nip at each other randomly. Otherwise they're completely fine with each other.