Hair Growth Remedies

I’m not talking a miracle hair growth vitamin or anything like that. I’m also not talking about something that would make my hair grow insanely fast because I know that’s not possible. I’m asking what vitamin, you know like A B C D ect… that would promote hair growth…my hair doesn’t grow at a normal rate these days and Im thinking that I may be missing something in my diet??? So what vitamin if any is know for promoting heathly hair growth and nail growth ect?

I lost the hair on the top of my hair due to radiation and I was wondering if there are any special treatments I can do to promote the hair growth.
Should I wash my hair more or less? Right now I have some dry scalp so I use an all natural itching/dandruff shampoo that has been helping. Also, I wash my head twice a week and use a soft bristle brush to remove the dead skin and stimulate blood flow to my scalp.
Any recommendations?