Do you have a QT tank? If so, I would recommend trying Kanaplex. It is specifically made for bacterial infections. If you don't have a QT, you can also use as a dip; however, if you have a lot of animals to treat that can be a major pain.
This 75 gal is a sick tank. These fish went through 35 days of Copper Power at the start of treatment. The fish then went through 3 consecutive treatments of Furan2. I then did 10 days of MetroPlex, KanaPlex, and Focus on the good advise of Humblefish and others here because the fish were still itching. I did some freshwater dips and then 10 days of General Cure. I stopped medicating the tank and added carbon to the HOB filter a little over a week ago. Today I did another freshwater dip on all fish and added Meth.Blue to the dip.
With so much treatment going on, the tank developed a bacterial bloom two weeks ago. I've been doing heavy water changes...even more than before, wiping down the glass and changing out the filters every other day. I do anywhere from 40 to 90% water changes, but the cloudy water just won't clear up. These fish have been through the ringer...and so have I at this point. I'm about ready to give up on the hobby. I feel like everything I've done and the ton of money I've spent trying to cure these fish was for nothing. They are all still itching. My efforts seem only to extend their lives a short time. The fish are still dying. My PH is 8.2, salinity is kept low at 30 because of the lower oxygen levels in the tank right now. I have two sponge air filters in the tank, a double bio-wheel HOB filter, and a powerhead agitating the surface even more.
Thanks for answering the post. While I've already tried what you suggested, it's nice to know someone cares enough to try to help. I fell pretty alone here. I don't even have anyone in my general area who keepd saltwater fish, so most of my fish are purchased online.