[You can pull out the Regal for treatment, but it is quite likely that the parasite is already in your substrate/LR and waiting for the opportunistic moment to grab the rest of your fish.
Untill you can get a larger QT set up, lets try a few other things first. As for a larger one, a large rubbermaid tub works great.
You can increase the temp in the main tank to about 82, no higher. The salinity can be lowered very slowly to about 1.022 if its at 1.025 right now. Be sure this change is done slowly over a matter of several hours.
You can soak all food in garlic supplement. I use the chopped garlic that comes in a jar near the produce section, just suck the juice out of the jar. You can also buy garlic at the LFS.
Check and see if your LFS carries Pepso food made by Jungle and feed it twice a day.
You probably wont see the parasites in the gills without taking the fish out and looking for them

,its very likely they are there though.
There is a good chance of nipping this in the bud without the hospital tank, but do get one running so you are ahead of the game. All of your fish are at risk, so its better to treat them all at the same time.
Hopefully one of your local reefers will have a refracto you can borrow just in case.
LOL! George, if I could think as fast as I type, I might be ahead of the game!]