Hi,
Welcome to the ehealthforum and I am really glad to help you out.
There can be many causes of hair fall and premature graying of hair and it could be nutrients and proteins deficiency in the hair cells, emotional or physical stress and dandruff. Other causes of premature graying of hair are an unclean condition of the scalp, washing the hair with hot water, drying it with an electric dryer, and use of hair dyes. Heredity is also a predisposing factor.
If there is or nutritional deficiency then give your diet an overhaul if you're lacking vital nutrients for growth and take some supplements.
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.