Update: Everyone is back in my display tank as of YESTERDAY!!!
It was a sad and long battle. I honestly would not do hyposalinity again. It was so stressful on the fish, myself, and my family. The amount of water changes and additional equipment was painful. A filter sponge was insufficient for this many fish. I had to get HOB filters, heaters, feed often to encoruage immune response, the tank would get cloudy, bacteria would cycle then die off in monster water changes. I was chasing ammonia and nitrates often. I was struggling to maintain pH and salinity because of evaporation and water changes. Things would normalize for a bit, maybe a week without a water change, and then it would get nuts all over again. Very painful when the ICH returned on week 4 and I had to keep everyone quarantined/hospitalized for an additional 4 weeks or so. That is pretty much what left the sour taste in my mouth. I lost two fish in the process, a cutie pie dottyback and a damsel.
Many fish started acting stir crazy and aggressive by week 4 or so, there was fighting and broken fins despite many, many PVC pipes and hiding places. I actually built stacked caves and got more PVC than pictured. I think I would definitely recommend copper which is only a 2-3 week treatment as far as I know. I wanted to hospitalize another week, but couldnt get the nitrites down, and needed to do 80% water changes towards the end. It was awful. Copper is the way to go IMO, but keep in mind, I was treating several fish, not 2 or 3. The bioload was just too much.
So, everyone who survived is doing well and so freggin thankful to be home in the DT. The fish who were terrorizing the others have stopped completely. There is fullfillment in their lives. lol.
Moral of the story: QT everything, and perhaps hyposalinity is inappropraite for more than 2-3 fish at a time due to bioload and length of time needed to complete treatment.
BTW, I wanted to give macro algae as someone mentioned here preventatively? Where can I get it and what kind should I get? Does saltwaterfish have it?