Well, I'm not so sure it's sour crop after all. This morning I found the Americana hen hunkered down on the floor of the coup, so I picked her up and felt her crop. Felt mushy, empty. But since she wasn't protesting me picking her up, I knew she wasn't well.
I took her into the isolation ward of the "hospital" and put her in a cage. I checked her a few minutes later and found she hadn't moved, but seemed to have fallen over on her side. I started to move her, when she began seizing, thrashing, throwing her head back. As first I wasn't sure what was happening so picked her up, and then quickly changed my hold as she lost her bowels and seemed to "throw up" as a clear liquid came out of her beak.
That fast she was dead. Still don't know what happened.
Now the first hen is standing up and moving around in her cage. I did try to put her back with the others but she wasn't too perky, so I immediately put her back in her cage where she has her own food and ACV-treated water.
Now sure what to do. Sure don't want to see this go through the entire flock.