um well ...
tell me if i'm missing something but
1. gold fish are COLD water fish and cichlids are Tropical water. that is why you should not keep them together.
2. If your gold fish is bigger than your cichlids than it is definetly to big for a 20 long.
3. cichlids are aggressive and i wouldn't rule out a cichlid attack here because he was kept with them.
4. if it is an injury from an attack... i'm not sure if this applies to fish or not salt for humans hurts very bad on wounds in fact is considered a torture ploy to make it hurt much much worse. so I know your doing salt baths but im curious how the fish is reacting.