Wow...I just read through some of the first posts and some recent ones up to the last ones, and I'm amazed at what a strong, wonderful and brave little hen Ivy and the other hens who are still holding on. I have a rooster named Ivory and if anything like that happened to him, I don't know how I would deal with it.
I feel much sadness and sympathy towards both all your hens that aren't feeling well and you. You're such as great chicky mom; you do what's right for your girls, but you also know when it's time to let go and when it's time to give them a 2nd chance (or in this case, a 3rd or 4th chance!). It's so kind and caring if you to give your girls a 2nd chance. For that faith you have, some or all of the sick hens might make it through because you spared their life instead of giving up on them.
I hope and pray that your poor little hens feel better soon and this will all pass soon and never happen again for you. If you lose a few because of it, just remember that you did all you could and are a great chicky mom.
You gave your girls one of the best lives a hen could ask for, and if/when they pass on, don't feel too bad about it. Obviously, you will be sad about it and I know how that feels. Trust me. But remember the happy memories you made with your hens and remember that they will be in a better, happier place and will be in peace at last.
Think about that and your sadness just might be replaced with relief and happiness; relief that their pain and suffering is over, and happiness that you had a chance to share your life with them and someday, hopefully, you will meet with them again.