I believe that is the likely end at this point. It would seem the infection had progressed too far before treatment began. Unfortunately, with fish illnesses, this is often the case. Illness mixed with poor water conditions are often too much for fish to overcome.
It is sad, but hopefully your able to learn something from the experience and are a better fishkeeper in the long term for it.
We've all been there before. It hurts, but if you learn something, there is some gain.