I looked at the first video of Coho--She is really pretty!
I've had birds die of of an internal fungal infection, and since have created a web page about treatments. If it might be of help, it's on my PoultryPedia.com website.
I've also had birds with Lymphoid Leukosis. Coho's symptoms & watching her behavior make me wonder if that's possibly what she might have instead??? If you want to look some up, there is info on that at:
How is Coho doing now??