It’s a good idea. Figure if meds all didn’t start to work then suggest some salt.Surprised no one thought of entertaining the idea of salt or salt baths...
Eitherway, good to hear hes getting better...
Fish maybe intolerant to meds. For sure the bgk will be. The other fish may have already been sick and medications probably added to them dying.
Would cont with what ur doing till all spots are gone.