It's REALLY important that you leave the temp at 86F f or a minimum of 7 days from the day you see the last ich spot. 10days is better. Remember the ich... protozoan can live in the tank even after it drops off the fish. That's why you don't want to rush this. If today was the last day you saw a spot, then don't start lowering the heat until next Saturday. Can't stress the extra days enough if you want to truly obliterate it.