It sounds like your fish were developing a bacterial infection that you caught in time and very likely, did as much if not more to halt the progress and cure with the fresh cooler water, than the meds.

All Goldies are cold water fish, even the fancies. To them, any temp above 55 deg., is pretty warm and the warmer the water, the faster bacteria grows and the less dissolved oxygen is available to the fish, and Goldies need a LOT of oxygen.

I haven't a clue as to why your Oranda developed black spots and streaks, unless it's blood that still needs to be absorbed. Or, it may just be showing it's mature coloring.

Nevertheless, as long as the fish are looking and acting healthy, don't give them anything but strong filtration, lots of fresh water and air, and they should be fine. I do not believe salt is good for them. Carp are totally FW fish and do not occuer in the wild in even brackish water.

Goldies are at the same time; the easiest and yet hardest of FW fish to keep in tanks, but the only real labor, is water changes, water changes, water changes.

BTW: once they mature, 20 gal. will be too small for 3 Goldies, each of which will represent the same bulk as at least 100 guppies.

If you enjoy your Goldies as much as I do mine (they tend to grow on one), and want to let them grow to their natural, mature size, while staying healthy and active, plan for no less than a 55 gal.

Thanks for the advice Birdwidow. Sorry I haven't been back to this website since I posted. The fish are doing fish. All the discoloration cleared up! There are only 2 fish in the 20 gallon. And yes..they will need another tank soon.
Thanks again for the advice.
ucguy101