Just a follow up -
the chick is actually doing better!
I thought it might be too much vitamin whatnot in their water (since that was the only thing i did differently with these chicks and all the others are growing beautifully) and yesterday was about to give her up for lost, but then the thought occurred to me to flush her with water. So I gave her water from a syringe (cause she wasn't eating or drinking) - lots of water from the syringe (over time), which she probably aspirated a bit of, and this morning she wasn't panting and was actually eating and drinking on her own! I'd given her up for lost, but we've had a little miracle -
I think we'll call her Millie for "Milagros" which is miracle in Spanish...