Looks to be some sorta parasite to my but to be safe slowly raise the temp up to 84f but raising it one degree an hour and soak the food in garlic juice or feed a few pellets of NLS Thera A+
5 gallon planted(6 Pygmy Cories, 1 Betta,and 2 ADFs)
10 gallon ( 12 Pygmy Cories and pair of Kribensis )