None of the meds you have there are for internal parasites. Personally, I'd crank the heat up to 86° and continue with the salt treatment in the QT tank (at 1 tbsp/5gal of water like you noted), and go get some PraziPro to treat internal parasites.
I suggest treating all 4 because that infected fish was in the aquarium with the healthy ones. A fish infected with internal parasites can defecate and the parasites will be in it.
Fish feeding off the substrate can consume the parasites while eating. Also the remaining 3 can look healthy now and won't show signs until later. I personally went through this with 4 EBJD a couple of years ago.
Thanks, what would you recommend for treating the tank? Is there a good med safe for clearing out internal parasites?