Google columnaris to see if that is indicative of what your molly has. If so, it is highly contagious and you could lose fish to it even without them showing symptoms first.
I would suggest a 50% water change on this tank.
And I agree that you need to stabilize your temperature. By not doing so, your fish are being unnecessarily stressed, which can lead to illness.
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.... ~