I have a two blue dwarf gouramis and one sunset dwarf. The two blue ones are healthy as ever, great color and very active. My sunset, however, has been getting skinnier and now his head looks really large with a small body. he doesn't really eat or swim around and hangs by the bottom of the tank. Can anyone tell me what's wrong with him? All my other fish are healthy and I do regular water changes. I also have not added any new fish in months. I know I need to take him out incase whatever he has is infectious, but I don't have a quarantine tank. Is there any way to nurse him back to health or is he a goner?