I will just say that I have used Marcyn Plus a couple times, to successfully cure popeye and also to cure fin rot . . .
it worked very well for thost two things, but I haven't used it to cure anything else
what I liked about Maracyn Plus was that it was easier to dose smaller tanks; the other Maracyn products come in 10G doses, but Maracyn Plus is a liquid and can be used for dosing 5G or even 2.5G tanks