First of all: no spanking! That will not help, and probably just make the situation worse. Try a water squirt-bottle. That works well for me.

From what you have described, it really does not sound like Tubby is doing anything all that bad. Mostly he just sniffs at her, and then she reacts, then sometimes a fight breaks out? It sounds pretty 50-50 to me, if not even a bit more her.

I can understand that you would be upset when he just attacks her for no apparent reason.........that;s not good. But it sounds like it mostly starts with sniffing and has gone from there.

I would definately take both of them to the vet to find out IF there is anything going-on medically. Maybe you are right about her smelling funny because she is sick. She may also be less tolorant of him if she feels bad.

If this is something that is fairly new behavior, then it's likely that something is going on with Peanut, and Tubby is just being curious/concerned, etc.

I don't remember how old both your kittys are, so there could be an age thing involved too. I have a 8 yr. old cat, and a 1 yr. old. There are times whe the older kitty gets REALLY annoyed with the younger one, because he wants to play, play, play. They then get into it, but that is pretty normal cat stuff.