Hair smells after having it straight for two weeks help

Okay so I am a curly headed girl and have thick 3c hair. I was blessed to have my hair look really good straight and have made a routine that prevents heat damage to my curls. The only downside I have is that my hair smells weird after washing. It’s like the straight hair smell lingers but like 2x worse. Almost giving off a mildew scent. The smell usually goes away fully after a week or two but I need it gone instantly it makes me pretty insecure when I go out because you can smell the scent off of me. I wash my hair like 4 times on wash day with cold water after straightening and make sure to put a hair mask in before washing but the smell still is there after washing and doing my curly hair routine and adding my products. Is there a way to stop my hair from smelling? like a hair mask I can put in after washing my hair? Does anyone else have this issue after having their hair straight and how do you get rid of the smell?