I can't figure out what's going on. For about the last week every one of our cats accept one, the long hair, has been having serious sneezing fits. I don't think they have colds. I've seen cats before when they have colds and their eyes aren't swelling up or anything like that. We haven't changed food or cat litter so I don't think it's allergies. Other than sneezing all the time they seem perfectly healthy. Any ideas?