Just in case Melafix won't work for the first few days, buy some real medicine against bacterial infections, because Melafix is made out of natural ingredients and isn't really killing off any bacteria, more like a tonic for the fish, to help them recover faster.
If you had ich, it's quite explainable that it passed so fast since you had quite high temperatures in your tank it sped up the life-cycle of the free swimming parasites and they died before reaching another host. In other words, your fishes' immune system dealt with all the infesting parasites on its own. Meaning that the water is perfect, and that you should try to meddle with it as little as possible
You have a great setup, so just take it easy, and leave the water temp alone (: At most you could add water that's a bit colder (1-2 degrees) than the general temp of the system. But if I were you, I'd test the water chemistry for pH, ammonia, nitrite and nitrate, to be sure that all is well (: