Problems with diarrhea!! Help

I have a cat that is 3 years old. Probably for the last 2 years she has had diarrhea on a regular basis. Its terrible, her butt is always dirty and she is a white long-haired cat and that makes it even worse. I have another cat that is prone to UTIs so I feed them a Urinary Tract health food, I feel like this is more serious than diarrhea but sometimes I wonder if she is allergic to something in the food. I need to know what kind of food to feed cats with both problems and also they are very picky, two weeks ago I tried to switch to Natural Balance, for the first time Stella was clean and didn't have diarrhea but my other cat wouldn't eat the food. What should I do???

Chronic diarrhea is a very real concern. When was the cat to the vet last? One of the problems with diarrhea is that dehydration and anemia can result from it. Not to mention how debilitating it is for the poor kitty who has to endure it. Your vet should be doing tests to find out the cause for the diarrhea and you should be pushing fluids so the kitty stays hydrated. If you have to feed separate foods, then do so. I would even suggest you start giving the cats filtered water with a few drops of GSE (Grapefruit Seed Extract) in the bowl to ward off the bad bacteria. But a vet visit is paramount for such long-term diarrhea-

I think maybe this sounded a lot more excessive than it really is. Stella does not have diarrhea everyday to the point of dehydration. And I didn't mean to sound like it wasn't a serious thing. My vet has not offered any solutions other that changing food,which I am trying to do. She does drink plenty of water, I have a fountain that both cats love. But I like to free feed and I don't know how I could get one to eat one food and not the other, they will eat which ever one they like. I feel like Stella may be allergic to something in the food that's why I am trying to find a more natural food without corn, dairy, or wheat. I've heard that those ingredients can cause stomach problems.
Please don't think I am not taking care of my cats, they are my babies. I just need to know what kind of premium cat food people with finicky cats are using.
Thanks

Hello,
Remember if you are changing foods alot, that can cause diarrhea. So when you change to a new food you have to mix it with old food until they are eating just the new food. You can check ingredents of cat foods on the internet (just search the company). I feed my inside cats dry food only, Nutro complete and Nutro Kitten, mixing the two since all the cats eat together. Nutro uses Rice and not corn. So check the labels. IF it continues try another vet.
Clara