Are you saying that you are treating your main tank with a copper medication as well as hyposalinity???? If so, you need to stop one or both immediately. You really need to get all your remaining fish out of your main and into QT
where you can treat with EITHER hypo or Cuppramine. Run carbon in your main to get as much copper out as possible and slowly raise the salinity to 1.024. You will need to leave your main fallow for 6-8 weeks to allow the parasite to run its life cycle and die off.
How big is your tank? What are you water parameters? How long has it been set up? Let us know and we will try and help.