Welcome to Heathcare Magic Physician's Desk!
He is having a general tired state may be due to excess enthusiastic workout, but diarrhea
also indicate towards some abdominal problem.
Get his blood pressure measured.
Start on OTC pantoprazole+domperidone
combination for nausea.
If he does not respond in a day or two get him examined physically by a clinician.
Wish you a great health!