My 8month old black/araucana hen, Penny, has a swollen head that is pale. Her comb is also pale. Beyond a puffy face, she is normal in every respect (eating, drinking, foraging, etc.). Her face has been swollen for almost 3 weeks. I have been adding vitamin/probiotic powder to the hens' water for about a week now. I have done endless searching on the Internet for clues as to what she has and how to treat it, but I haven't found anything close. She does not have trouble breathing, she doesn't smell, no watery eyes or runny nose. The only difference from her and my other hens is her puffy head. Her head seems to run warmer than my other hens. My other two black hens (same age, same brood) just started laying. We have gotten a few soft-shell eggs in the coop, and I'm pretty sure those belong to Penny. I feed my hens a local non-soy, non-corn pellet food, plus some corn scratch every once and a while, oyster shell, and then whatever they find in the yard. Their bedding is straw and wood chips that is cleaned on a regular basis. What is wrong with my hen and what can I do? Thank you for your help.