I'm so glad kitty is feeling better! I know you are relieved!
Yes, DO NOT change back! I made that mistake and when Big Boy started his "antics" of trying to pee, it broke my heart. Guess we live and learn, right??
And other kitty should be fine. We started Big Boy on Science Diet Prescription C/D, but got an ok from the vet to switch to W/D (weight control---it's not working for the weight lol). The food is fine with both the cats and no UTI in 9 years.