I think my gluten intolerance actually started after my C. diff infection during undergrad about 6 years ago. Still can't eat gluten containing foods to this day. It's important to remember that antibiotics that are decent at killing C. diff aren't always effective because of resistant strains. Having said that, if he no longer has C. diff but still has symptoms I would hit it heavy with the probiotics. C. diff and the antibiotics used to treat it can cause GI symptoms for months (I've been taught it can cause issues for almost a year, even), because you need to establish regular gut flora again. Probiotics have also been shown to reduce recurrent C. diff infections.