Hi, I'm just a noob here, but I think you shouldn't do complete water change, maybe about 50% at a time? My advice is if you really want to keep them alive for a time being you should buy test kit, that way theoretically you could know when and how much you should do water change, and don't overfeed them.I do partial water changes every morning because sometimes my naughty little brother tries feeding them when I am not looking and it fouls up the water (he was the one that caught them with a net). I have done complete waterchanges only once in the past six days since I got them. Also, if these fishes are of the ame species as Phoenixkingz said above, then they still haven't developed any scales for it to stick out if by chance it was actually dropsy.