Thanks for your responses! I'm totally new to raising chickens, so any advice is very much appreciated!
When I went back out tonight to check on the chickens, I noticed that three have swollen/hard feeling chests. The sussex's is so huge I can't believe she can walk upright! I let them out for a few hours to graze in the yard, so maybe they ate too much? Will check on them again in the morning. All five are acting normal and they all laid today, so hopefully the swelling goes down overnight.
I have noticed in the past few days that some of the hens have been having runny stools. I wonder if this is a symptom of an impacted crop? None of the hens smell, as far as I can tell.
I saw on the link that many people give their hens yogurt and scrambled eggs. Others held their hens upside down and massaged the crops. Anyone have advice about something that's worked?
Thanks again!