I have 8 chicks that are 8-9 weeks. One is a Australorp, 4 are Production Reds and 3 are Barred Rocks. They were all the same size when i got them but the Australorp and PRs passed the Barred Rocks up and are about twice the size. Everyone seems happy and healthy. This picture is from about 2 weeks ago and everyone has gotton bigger but the Barred Rocks are still about half the size.