I suspected it was a respiratory disease like I mentioned in post #15. I highly recommend that you cull her immediately and bury far away from your coop or incinerate her. You're risking the chance that it will spread to your other birds.
We put her down today and will be sending her for a necropsy on Monday. I really wanted her to get better but it was finally clear that she wasn't going to.
Would treating the others with the Duramycin as a preventative do more harm than good - build up a resistance?
I would not treat the others if they they don't have symptoms.
-Kathy