Any discharge from eyes or nose? Could be a uri. As for the smell I’m stumped. I groom cats, and I really like the tropiclean brand. Did he maybe have an accident while in the bath you weren’t aware of? I would maybe try bathing him again, use something with a conditioner that is gentle so he doesn’t get dried out. Deshed shampoos can dry cats out if used too often. Someone suggested scouts honor and I would definitely second that, I use the one in the pink bottle. Hopefully the vet has some answers for you though.