What Causes Bad Odour In The Scalp?

Hello. I am a 31 YR Female. 250 pounds, only health issue I have is low vitamin D levels. About 17 I was told. I have a sour smell that emits from my scalp, even after washing the hair it comes back within a few hours. My question is how can I get rid of this smell. I have tried dandruff shampoos, tea tree shampoos, sugarless grapefruit juice, baking soda. Nothing works