I'm so so sorry that you're going through this. It does sound a lot like fish TB in what you describe. I can imagine that it is very difficult to watch, and heart-wrenching since there's no cure. You're doing all that you can, and have provided them with a wonderful, loving home.

Is the tank they're in now acrylic?

Yes, if they all pass (hopefully they don't), then I would recommend nuking the tank and starting the cycle from scratch. It is a long process, but certain things (like maybe seeded floss from a friend's tank, or BioSpira) can help. Yes, you can bleach dip the plants; I'm unsure about TB and plants, but Barb may be able to shed some light.

*hugs*

~Ash