Glenda, your little fish is probably a female and has been run ragged by the males, just as you suspected. She could discharge her eggs in the isolation tank, but if there is no male around to fertilise them as they are discharged, they will not be viable. Part of the male fish's job is to nudge the female fishes abdomen to encourage the eggs to be discharged. Having her on her own she could become egg bound. You could, if you hold her, gentle massage her abdomen, to help her spawn her eggs. It maybe better however, to add one male to the isolation tank and keep an eye on the "goings on". You can hang a string mop-head or a cut up hank of wool, into the water for her to spawn onto. Once she spawns remove the male. Let her rest up until her bumps and bruises heal. "Horton"

I have heard that Shubunkins can change or lose colors but it seems odd that the change would be so sudden. My only Shubunkin, Spot, started out as a red and black calico. Now he's practically all red except for one spot on his nose! Guess he wanted to be more like the other guys (all red comets) LOL. If chameleons can change color why not fish? Who knows!

I went through a similar experience after purchasing goldfish from and on line vendor but they were being held in quarantine in a 400 gallon pond when they started displaying nearly the same symptoms and resulting death. I determined that my fish were suffering from some unknown parasite. I used Proform C which is a broad spectrum malachite green & formalin treatment which will eliminate nearly all parasites that afflict goldfish or Koi. Read the directions carefully and treat your whole pond three times doing water changes between treatments. Worked wonders for me and came very highly recommended at that time. I tried salt myself and they still kept dieing since salt is only effective for a few parasites why waste your time. Once treated as prescribed you will not need to drain the pond since all parasites should be eliminated. It is important to have a fairly accurate knowledge of the volume of your pond. One quart will be enough with plenty to spare. Let us know how it all is resolved. I was so happy that I quarantined these fish and not released them into my main pond of 8000 gallons with many other fish until I determined they were healthy and free of parasites.

I had some baby "goldfish" that spawned in my pond, and it was only a year later I noticed they all had barbells and were actually baby Koi! Made me very happy as I had just lost their dad to illness. They sorta look like him too, just not as bright a color. But I love em all none the less.