With 2 gallons and no filter, you should be doing daily or every other day 50% water changes.
Your temp is too low, too.
What does this mean? "Ive been adding the same treatment to the tank every three to four weeks"
75: blood parrots, featherfin cat, emperor tetras, turquoise rainbowfish, BN plecos, japanese trapdoor; 46: WCMM, gold inca snails, ghost, bamboo & amano shrimp, kuhli loaches, rummynose & ember tetras, endlers, platies, flame gourami, guppies; 16: pygmy, peppered, loxozonus corys, otos, assassins, RCS ... ~ Research PRIOR to purchase.... ~