Try and isolate him if you can. The dropsy itself is a symptom of a bacterial disease of the kidney, and though not contagious in itself you dont want the other fish picking at it when it does.
You need to up your cleaning of the tank, can you give us more info such as gallonage, filtration and how often and how much in water changes? Have you tested recently for ammonia, nitrites, nitrates and ph?
As for the fish, once you see the pineconing its often too advanced to do anything for. If you have a spare tank and heater then raise the temp slowly to 80f and add 1/8th of a teaspoon of epsom salt per gallon.
Sorry but it doesnt look good.