I do believe I jinxed myself. Went down to tuck in the chicks that I haven't kicked outside yet and I could hear one of the buff cochin bantams breathing from across the room. Caught her up, felt the rattle in the chest. Opened the mouth and there's phlegmmy stuff in the back. They always do this when the stores are closed, don't they? Luckily I've already been caught out and had some oxytetracycline powder in my emergency kit so started her on that...apparently Tylan 50 is better according to my searches, but it will have to do until morning. Have her in a small animal carrier that I could set in the brooder with everybody else...she was panicking being away from the flock. Since they're all likely exposed already anyway
I'll probably do a full brooder clean out tomorrow too...just in case some of the bedding has gotten moldy or something. Yay.