Have you tried giving him any probiotics? If he had excess bacteria in his stool, then he has an imbalance and he needs to good bacteria put back in. Especially now that he was on an antibiotic and further killed off the good bacteria.
What kibble are you feeding him? Have you had him tested for allergies? Food allergies actually only account for 10% of all allergies.
~The strength of one's opinion should not exceed their knowledge on the matter~