Animals can get food allergies as they get older and some pets
can't eat the same food as the rest of their family . You could try feeding your cat another cat food and see if that help. You will need to do it slowly by adding a little new food to food the cat it now eating . Check out what ingredients are in the cat food you're using now and see if anything can cause diarrhea. Flax seeds are a lot pet foods and this will made a pet poop more.