Premature Greying of hair

Patient: HiI am Anees and I am 24 yrs old. I have been facing premature greying of hair from last 4 yrs.I consulted a doctor and he recommended me Keraglo Forte for 6 months. I had these tablets for 6 months and then when i visited the same doctor again and asked him that it didnt help, he recommended me Hautvit for another 6 months and a herbal hair oil.I have been taking these for 3 months but i dont think there is much of an impact on my hair.Plz advise