The biggest problem with most health issues in fish is without having a necropsy performed, and putting samples under a microscope, it can sometimes be next to impossible to know with any certainty what the correct action should be.
When I looked at your GT, it appears to be shedding the lining of its intestinal tract, which generally is caused from internal parasites of one form or another. Typically it will be caused from spironucleus vortens, which the 3% epsom salt soaked pellets should successfully eradicate within a few days. But, that's just a guess, and may or may not work in this case. So far I'd say you have been lucky as your fish are all still eating, which is definitely a good sign, and definitely makes treatment easier.
Good luck, and keep us posted.
When I looked at your GT, it appears to be shedding the lining of its intestinal tract, which generally is caused from internal parasites of one form or another. Typically it will be caused from spironucleus vortens, which the 3% epsom salt soaked pellets should successfully eradicate within a few days. But, that's just a guess, and may or may not work in this case. So far I'd say you have been lucky as your fish are all still eating, which is definitely a good sign, and definitely makes treatment easier.
Good luck, and keep us posted.