I bough a gorgeous Copper Maran hen this summer. She is about a year and a half old hen laying big brown speckled eggs. The egg is always the same size, color, and texture and it appears every 48 hours like clockwork. I noticed 4 days ago that the area below her vent is swollen, firm, and puffy. The swollen area seems to be more pronounced and bigger as the days pass. That's all that seems wrong with her. There's no redness, heat, evidence of picking by other chickens, signs of lice/mites/, no sinus discharge or breathing difficulties. Her vent is normal looking when compared to the other laying hens. She roosts at night in one of the nesting boxes. She's not molting as her clutch mate is. She is heavy, meaty and docile when I pick her up to examine her. Her eyes, comb, wattles, and feathers are bright and healthy. Her poo is watery but that may be from eating greens from my big home garden. She and the other hens free range in lots of grass and brush which they all eat with gusto. Can you offer ideas for me to investigate? I was wondering if egg yolk peritonitis can cause this kind of swelling and no other apparent symptoms. Thanks for any ideas/wisdom you can offer! I'm at a dead end for issues to investigate.