Possible solutions to this is I would go through and try to pick some of this dead stuff and simply just try to air it out. If this was growing in my greenhouse and I got it to look like this, I would just dry it out. You can do this at home. If it has a good root cube still sitting there, you can just let the root dry. Try to clean it up. I could treat it with a fungicide but I think at home that's not really practical Here's another example of being over watered. This is a begonia. It looks terrible but I think the same thing goes. I think it would have a multiple problem. I think that it was over watered and in too much sun. See these roots, they are turning all brown. It's really not happy. I think if I put it in less sunlight and let the roots dry out for a few days. I think we could get the plant recovered. As bad as it looks, it still has some good leaves and I see some sprouts in here. See, I think it would be all right. It just needs to be treated nicely. Too much water.