My son has successfully completed most of his strenuous training for the US Army Infantry. At his latest course he became immediately dehydrated (early in the day after plenty of fluids) and his kidneys shut down (with all the vomiting, fatigue, elevated heart rate and cramping). His core temperature never exceeded 99 degrees and neither of the two times this has happened were classified as heat incidents. The Army doctors tell him to drink more. I think something else is wrong. Any thoughts?