Hi I've noticed this red marking on one of my chicks. She is 28 weeks and has alwAys has a bare behind. She is the head of the pecking order. I have never seen her feathers getting pecked or have ever found any feathers from her in the coop or pen. I wonder if she is removing her own small feathers before they have grown? Or could it be red mite. I have no obvious signs of red mite and the other hens I have seem ok. This hen has been my best layer but has had a problem for the last 5 days with no shell eggs or no egg at all....any ideas