We let our fish-house tanks stay natural temps and just heat and cool the entire building rather than the majority of the tanks. (with exception of a few that need specialized temps of course.)
Mollies seem to do fine in the upper 70s lower 80s farenheit (77-82, 82 being the max high I would really take them to) You did awesome by the way, when you noticed something was not right and fixed the problem right away, congrats.

If the parasite suspect is
ICH you could also try increased waterchanges, 50% daily for a week, and keep the fish as happy as possible. (If they get stressed their immune system (slime coat) gets compromised easier, which is how the parasites attach to the fish.) Good luck.
