Hey there and welcome to this site. Lots of great information from very supportive people. That being said, can I ask a few more questions? How old is he? When did his symptoms start - in July, when he went to that academy, before, or after? Has he ever had gastrointestinal ailments previously? How often does he have diarrhea (D)? Is there ever blood in it? Does he have any other symptoms? What's his diet like?
You say he had an upper GI series/small bowel follow through (SBFT) and that test can be a good one to detect more serious abnormalities, but has the GI doc mentioned anything about a colonoscopy? If he's having the big D, especially bloody D, he should probably get a scoping...also I think this is even more important since they found that he is anemic. Anemia can be caused by a poor diet, and so can diarrhea, but things like inflammatory bowel disease can also cause diarrhea and anemia, so it's always good to have it checked out a bit further.
Let us know how you and he are doing!