Talk to Dermatologist on Coarse Hair

I had hair botox/keratin 3 years ago my hair were frizzy naturally but its been years and they have not been returned to their original condition again after that, the new hair growing are very coarse and wire like specially in the top layer of hair im also getting a lot of grey hair on the front i dont have them genetically, the hair texture is like if i glide my finger on a hair it feels like it has knots now i have no idea what type of doctor should i see a dermatologist or nutritionist or some other kind of specialist because im not sure about the cause i have never seen anyone's hair like this