I just euthanized Holly. :(
He was such a fighter. He would get a bit better and then get ten times worse. This week, he stopped eating and the few times he did eat, he regurgitated it a few minutes later. He also developed a couple of lumps/tumours and had barely any blue left on him as the white/colourless patches kept spreading. It was almost like he went see-through. I thought he was dead a few times as he was just laying on the bottom of the tank with no gill movement or anything for 5 minutes at a time. If I tapped the tank he would move slightly though. I thought it was time to put him out of his misery.
Poor Holly. I tried everything I could but I couldn't make him better. He was such a fighter, but whatever he had was just too strong.
Thank you all for your help. I really appreciated it all.