your symptoms can be due to telogen effluvium. The growth cycle of hair is in two phases, anagen or growth phase and telogen or resting phase. During stress or when the immune system of the body is lowered many hair enter the telogen phase at the same time and can be shed. Hair takes between 3 and 6 months to re-enter into growth phase, so the restoration is a bit slow.
Eat a healthy balanced meal, use mild shampoo and lather gently and rub gently with towel to dry his hair. Try and avoid using blow dryers. Biotin is present in foods like eggs and liver. So in addition to these foods, biotin supplements can be taken after a trichologist’s prescription.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.