Try the hairball formulas. I tried that with CJ and it helped immensely! Even now that he's taking the pred. he still gets major diarrhea if I give him regular food instead of the hairball formula. He gets Science Diet Senior Hairball formula. He loves it and it really helped.

Like I said, sometimes these issues take awhile to clear up. I don't think that your vet is trying to mask the problem, just giving you some ideas to try to help them get back to their normal "cycle." If there are no parasites present, it's really difficult to figure out why cats experience diarrhea and a lot of times it will just go on the record as "idiopathec diarrhea" which means they haven't got a clue why it's happening, so getting an absolute definite reason why your two are experincing this might never happen.

Also, it's not unheard of that cats develop an allergy to foods they have been eating with no prior problems. I know Jenluckenbach was also experiencing this same frustration with one of her kitties, so you could do a search to see what finally worked for her.

Like I said, it takes time. We humans are always so impatient and we want to see immediate results. Unfortunately, these diarrhea problems don't cooperate as fast as we humans would like them to, and it's so very frustrating for us, but we have to learn patience.