Yes to raising the temp but no salt. This is only a second option if needed. And yes, salt does harm fish. Soft water fish are more susceptible than hard water, but salt does negatively impact a fish and unless it is the safest and most effective treatment for "x" do not use it. I have an article on two sites:
Many years ago, 1990's in fact, I killed fish using so-called ich medications because I did not understand the effect these things have on many fish like characins.
I have seen ich spots suddenly disappear, it may be this or something else. I wouldn't worry. The heat is not going to substantially harm these fish.
Healthy fish will not succumb to ich, it only occurs when the fish are stressed. I use a 20g tank permanently running as a quarantine for new fish acquisitions, and more than once I have spotted ich on the new fish, but without doing anything even not increasing heat they fought it off and it never returned. This is one advantage of having a permanently-running QT, it is like an established tank (mine has sand, plants, thick with floating plants, and a couple chunks of bogwood) which means the fish are immediately in a better environment and thus reduced stress.
