I have noticed a few times when I have been looking at my chickens that they have a yellowish tint on there waddles. It looked almost looks like powder but doesn't rub off. I keep the coop clean they have plenty of room and free range. I wish I had a picture to post with my question. It's not on the entire waddle and I haven't noticed it on the combs. It's usually closer near its feathers and will cover a small noticeable section of the waddle. I have tried to research it but haven't seen anything like it.