Cat had surgery and now specifically dislikes 2 of our other cats.
We have 5 cats. Our eldest orange cat who we have had for over a decade, 2 female cats we got from the shelter together a few years ago, and 2 orange brothers who we found as kittens about 2 years ago. One of the female cats had surgery to remove a growth on her soft palate. Brought her home the same day and kept her separated for a couple days to recover and so we could more easily give her the steroids the vet prescribed. We then let her back out into the house with the rest of the cats and she was fine for a while until she attacked one of orange brothers. We got them apart but not long after she went for him again and we put her back in confinement.
The vet figured she was probably aggressive because of the steroids so they lowered the amount she was being given and she seemed fine. The orange she attacked, however, was not happy and kept hissing even as we tried slowly reintroducing them with scents and feeding them near each other through the door. She showed no aggression and after a week the orange boy was still hostile so we tried swapping them, letting her roam the house while the orange was separated.
Once again she was fine for a while but then went after the other orange brother who had done nothing, was just laying down sleeping. So we put her back in confinement alone.
We are at a loss for why she is doing this. She hasn't shown any aggression towards our older guy or the female we got her with. Just the 2 brothers. They are newer to the house but they've all been fine together for a few years now. And like I said she seemed to have mellowed out with the other orange that was rightfully upset with her and then she just randomly attacked the brother.
Anyone got a clue as to why she is doing this or how we could fix it? She is off the medication, we have been reintroducing for over a week, and her behavior seems targeted and yet erratic. So we are just confused.