Felidae update

Back in August I sang the praises of a cat food called Felidae. (old felidae post) It had succeeded in keeping my cat, Midnight, free from uninary track infections. Recently we added their wet food to the dry food and bam! He got another infection. Somehow we were doing alright with just the dry which is ironic because the moisture is supposed to be better for him. So back to our vet prescribed Royal Canin Urinary SO for felines it is. What else can we do?!