Ah sorry to hear that we'll at least you know now. Like I said before if I were you I would treat the tank. Dropsy is cause by many different things but once they start showing the signs it's already to late 99% of the time. I would get a broad spectrum antibiotic and aquarium salt. Antibiotic should kill anything that is wrong inside of them and salt is just all around good. Just make sure you do the right dosage and water changes every few days. But once again that's me other people will tell you different ways to treat the tank.