What happens if spa day doesn’t work?

Pit sweat has ruined most of my favorite t-shirts and even sweaters, so I did a spa day with the worst of them with 365 unscented powder (L, O, A) and then washed with the ammonia as instructed. Coming out of the wash they smelled neutral/nice in the pits, so I went ahead and dried them in the dryer (there was also no other option because it was raining and I do not have any place to hang the clothes). Upon drying, they smelled perfectly fine and I was excited that it worked, but 4-5 days later, hanging in my closet, the mildew smell was back in the pits, as usual. They failed the test of time.

Does anyone know why the bad smell isn’t there until several days after being laundered? And also why spa day failed to work for most of the shirts?

Whenever I wash my sweaty-pit clothes, if there was even a hint of B.O., it will later smell like burnt crayon mildew, which is the hardest smell to get out of my clothes that I’ve ever encountered. I don’t use stick deoderant—-I switched to spray when I thought it was the coconut oil from natural deodorants causing the mildew smell. I’ve tried using everything—vinegar, vodka, etc. (I stay away from anything with toxic chemicals, though, which means most products on here I can’t use).

Anyone else have this issue?