I'm sorry. I'm sure doing all that you can.Hi- she is turning one this week! I am still getting fluids and food down her- she is listless and now pooping watery green - not yellow. Just breaks my heart. I did contact “call a vet” - they were great, said it may NOT be blackhead - said I should cull her and get an autopsy. But we do have wild turkey and peacock in our fields that we could have tracked in their feces without knowing it and they seem to be the worst carriers...BUT I am the die-hard naturalist who wants to “wait and see” always hoping we can turn it around.
I'd try giving her some nutri-drench and scrambled eggs. If she doesn't improve quickly, you may need to put her down.
If so, I would have an autopsy, if possible. Are the rest of your flock showing any symptoms?
You will find a lot of good information here 
