It could be those exercise shoes. If the shoes themselves smell bad, get rid of them. Start with fresh shoes, use foot powder and get a set of new, white socks that you can bleach in the wash.
I had this problem a few years ago with a pair of dance sneakers. They got a bit...mushroomy, which is odd since I am a fastidiously clean person and never wear any type of dance shoes as streetwear. No matter what I tried with respect to cleaning and drying the shoes, nothing really helped much until I just plain got rid of them.
You might want to try soaking your feet too. A friend of mine has chronic foot fungus problems, but he has found great relief by soaking his feet in very warm water with a cup or so of apple cider vinegar. This seems to help him more than the commercial sprays and creams that he has tried.
Dances: salsa (standard/LA), casino, rueda de casino, cumbia Colombiana, bachata, mambo, cha-cha-chá, merengue, reggaetón.
Currently learning: Mexican cumbia, danzón, Cuban rumba
Dances to Learn in the future: flamenco, tango Argentino, samba, belly dancing, bhangra, ballroom rumba
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