They are about 9 weeks old. We were looking for the characteristic green of the bile sack, but couldn't find it...it was really weird. My husband thought he had burst it on accident. We had a few where the inside of the chicken looked normal, but a few where we couldn't see the bile sack even before we had messed around the inside. I thought I found an empty one-it looked like a clear sack attached to the liver-but why would a bile sack be empty? We didn't open the gizzard, so I don't know if it was green.
We're doing the other half today, so I will do some further investigating if we come across any others.