Coach,
I'd look at the insulin resistance/ pre-diabetes angle here.
Did they check his A1C?
Your runner could just be magnesium depleted, which would impair insulin and glycolysis. In other words, he may be fine generating ATP until forced to push to 95-100% VO2peak, in a XC race this would correspond to ~5' -6' into the event. In this scenario, iron overload would be a big mistake due to the oxidant activity.
https://www.ncbi.nlm.nih.gov/pubmed/15319146/
http://nutritionfacts.org/topics/diabetes
dsrunner