My son is 17 and short. he ensures to get 8 hours, exercises and has a balanced diet. how can i help him? i am already giving him vitamin d and b tablets, might there be a supplement to stimulate growth? thank you?

Any potential for further growth would be evident on a simple x-ray of his wrist/hand. That site has dozens of growth plates that have been studied over the years & give reliable estimates of bone maturity. If his bone maturity matches his age & the growth centers are closed he is done growing taller. Most males close growth centers by 17. If open, good diet, sleep & exercise maximize growth.