hills prescription diet

My 6 month old male kitten has had loose stool forever. He has been extensively de-wormed and has been on anti-biotics twice for a high bacteria load in his stool. He finally got better and had some solid poo. I was so relieved. I have been feeding him Innova Evo for the last part of the ordeal. I also wanted to give my cats Hill's Prescription Diet T/D. It is supposed to be great for their teeth. Whenever I give him even one ball of this food or any other kind his next poo is runny! Is is possible that he is really sensitive to corn and that is causing the problem?