If those are the only options then I'd go with the hyposalinity if it is indeed ich and not simple paranoia
Just be very careful to read and follow the instructions in the link provided. Remember that all
fish need to be treated for long term effectiveness. If you treat only the one fish, the others in the tank are still at risk of the subsequent theronts
as they emerge from their reproductive cysts. Before you take any additional action, please be sure of what you are treating!!
GreenEx contains malachite green and quinine hydrochloride, not what I'd consider very friendly ingredient and not always very effective.