I thought I had updated in here.
She's doing pretty well considering, but it's been a bumpy ride. After keeping her separated for a couple of days, she went back with the others. They must have picked on her and her eyes got worse - I realized she didn't come for treats and found her huddled in the coop. I brought her in and she was completely blind I think, both eyes heavily covered in scabs.
Kept her alone this time. She wouldn't eat or drink and was pretty weak. I've been dipping her beak to get her to drink and feeding her from a syringe, which she hates, but yesterday she started opening her beak - sometimes - to take the food. I squirt in a bit and let her swallow it.
I've been feeding her mashed egg yolk with a little rooster booster vitamins added. I was using water to thin but switched to sweetened condensed milk. She's putting on a tiny bit of weight I think.
She sleeps quite a bit, but the last couple of days she's been getting up and walking around in circles. She preens her feathers and stays clean. She makes chirpy happy-chick sounds the whole time she's awake. She won't/can't eat or drink on her own yet. Today the scabs are gone from one eye, but the eye is still closed. I think she's on the mend and doing well enough. I hope she can see again soon.
My favorite chick, a bright little BO girl (I'm assuming I know the sexes and hope I'm right on all of them) also got a scabby eye the other day. She's very smart, and quick, and observant though, and the other eye is fine so far, no one picks on her, so for now just letting her be.
The hen who raised them was very lethargic the other day, and I was really worried about her. But she showed no outward signs of anything wrong. After a day or so she's active again, though not her normal mean-bossy self and using a different call when I give treats - I think her usual noise is a warning to the others. But I hope she will be ok.
I'm really at a loss. In a few months with a flock of 16 at most (12 now since we lost 4 chicks to coccidiosis or early fowl pox) ... I've dealt with leg mites, coccidiosis, fowl pox, and not entirely sure everyone's respiratory is completely healthy.
I've raised chickens before much larger flocks for years, and have dealt with accidents and predators, but almost never sickness, and never THESE sicknesses. It's almost discouraging. The coop and run are like Fort Knox - we wanted to prevent losses and problems such as we've had before. Now I feel like I've just traded in for a new set of problems.
But anyway, I hope we get over the current bump. I hope soon too. It's very hot, and I need to get back to work (I've missed most of a year due to serious medical issues of my own, but I'm finally able to work again. But I can't leave the chick in a closed garage all day with no one to make her drink. I can't bring her in the house because of the cat. So ... I hope she will be able to see again soon. But in the meantime, it IS very satisfying to hear all the happy little purring chirps every time I go out there.

And I hope none of the others get this sick!