I had the same problem with my frog and unfortunately I couldn't get to a vet before he died. It is possible that it was passed to all other frogs in your tank. I would separate them all and see how it goes. If they are contaminated at least it will spare those who weren't. I don't know what causes it but it's a horrible thing to witness. I think without a vet there isn't much you can do. Sorry man and good luck!!