If the AQS doesn't help you can get Maracide or Coppersafe. Both are liquid medication for external parasites.. Maracide is for the use of a hospital tank and Coppersafe is best used for treatment inside the home tank. I believe Coppersafe will treat everything in the tank and not just the fish itself. It kills anything inside the filter and on decorations.
I have both medications but only have used Maracide, but they work in similar ways. Coppersafe will treat the tank for 1 full month at 1 tsp per 4 gallons of water and you're not supposed to do water changes during this time.
That may be your best bet if the salt does not work.