Dropsy Issue

[JessicaMarie421]

I need help! Last week one of my platies died from dropsy. I didn't catch it in time to save him, but I did a 50% water change & treated the tank with Maracyn-Two in hopes of preventing any of my other fish from dying too. I gave the last treatment today, & now my dwarf gourami is showing the same symptoms (swollen, scales protruding). I did a 30% water change & added some more aquarium salt, but I am at a loss for what else to do. Any suggestions would be great. I've never had an issue with any of my tropical fish before now, & I've been keeping fish for about 5 years.