Well, the salt IS going to be bad for your plants. I think the 84° should be enough to wipe out the ich fairly quickly, even without salt additions. It worked for me without salt. I got some infected fish from the LFS. In a couple of days one or two of my cardinal tetras had ich also, so I went to 84° which wiped out all of the ich in one day.
Why do you think you got ich in the first place? Is there something unhealthy about your tank? Did you bring in some infected fish?
If the 84° does not wipe out your ich quickly, you probably have something else going on that makes your fish's immune systems a little down. In my more inexperienced days, I replaced evaporated water with tap water each day. My water hardness went up and up until my fish (mostly tetras) were easily infected with ich. Once I switched over to RO water for evaporation replacement and my hardness went down to reasonable levels (it was 30 to 40GH at one point!), my fish are pretty much immune to ich now.