My 2 year old hen has a large swelling below her vent- like about 3" diameter. It looks like an egg is stuck in there- the skin is stretched out. Her vent was not blocked, but there was dried green/white poop which I washed off. She is acting fine. Any ideas what this might be and how I should treat her? Can an egg get stuck in there- she's been laying Jumbo eggs for a long time with no problem. She is a Barred Rock. Thank you for any advice!