I have one that's been living in the dark for about a month now and might actually be getting better!Great information posted already. I'll just add or reaffirm, based on our experience with a Mille Fleur bantam, to:
1). Keep her in the dark 24/7 for at least 2 weeks...longer if possible
2). Feed her low protein food such as millet bird seed mix...not BOSS. This is to discourage laying. I wouldn't use layer feed because you don't want to stimulate laying.
3). Squirt cream Prep H into booty each morning.
4). Add calcium to her diet.
5). Put her on an antibiotic
Our bantam came through it and now has hatched two broods. Good luck!
-Kathy