I've got a 6 week old Orpington chick that has a strange swelling on half of her head. It's not soft or weeping, and seems to be making her face crooked and deformed, and her eye is bulging out. She's eating and drinking fine, and is very active and is very friendly and social. This started when she was a week or two old and is getting worse. I've attached a couple of pictures. Any ideas?