Gaping at the surface followed by lethargy, lack of appetite and eventual loss of life are all symptoms of fluke infestation. I would definitely hit both tanks with prazi after you are sure that everything else has been filtered out. You might want to wait on the hospital tank until you are sure that the danger of costia is past. I would still increase aeration to the tank if possible. Certain mixes of medication can cut the available oxygen available in the tank. I don't think prazi is one, but it never hurts to give a little more air when possible. Stringy poop can be a sign of parasites, so give it a whirl and see if she does any better. Another option is to give her a smashed up green pea. That cleans them out, and they really, really like them. It's like a feeding frenzy in my tanks when I put peas ( or really any other veggie or fruit) in the tank! If they won't eat, you might try putting a little garlic powder on them. For whatever reason, it tends to make food more appealing to goldies, and some people believe it has the same antibiotic affect that it has on people.
I really wish someone else would jump in here and correct me if I am giving wrong information, but I think I am on point for the most part.
I really wish someone else would jump in here and correct me if I am giving wrong information, but I think I am on point for the most part.