RESOLVED:
Hi, guys. I tried to update my thread name at the top to "Resolved," but couldn't seem to find the option to edit it. Just wanted to post that I was able to take "Baby" to a vet, and seem to have gotten an answer. I was both right and wrong. Really good to know that it's nothing communicable and the rest of my flock is safe, but I'll have to put Baby down shortly. Heart, lungs, air sacs all sounded good, nothing felt lodged in the trachea and didn't find any fungal nodules, but it's most likely either
tracheal hypoplasia or laryngeal paralysis, meaning the flap that is supposed to be opening to let air into her trachea is being paralyzed or something in there is collapsing and will most likely cease providing her enough air in either an acute event or progressively. Congenital defect, pretty rare, but she's out in the yard looking content being a chicken, and I'll take care of her when she needs it.
Thanks again for all the info and support!! It really helps knowing you fine knowledgeable folks are here.
