We have 2 female siblings that are about 4 years old now. Same litter, both fixed and rescued from the shelter as puppies. The last few months have they started fighting more and more, each fight seems to be getting more aggressive. Constantly growling at each other, they finally had a huge fight today. Both bloody and limping. The more I read on it, it seems like they shouldn’t have been housed together to begin with. What can we do?