Opened coop this morning and found 10 month-old RIR dead under roost. This is my first flock and first loss. 4 girls, same age: 1 BO, 1 PBR, 1 silkie, 1 RIR. Everyone gets along, 20 sq. ft. coop, 60 sq. ft. run, layer crumbles plus oyster shells and grit free offer. BO and PBR started squatting & laying @ 5-6 months. Silkie not laying yet. RIR no squarting, no eggs. Assumed she was a late bloomer and then winter hit and wasn't expecting eggs anytime soon. She was always thinner than BO and PBR, but normal eating/pooing. 35-40 degrees overnight, not that cold. I usually check chicken vents once a week and noticed Ruby's (RIR) vent had started looking more like the laying vents. Yesterday she ate/drank and had dust bath with others. However, she wasn't as energetic as usual...normally doesn't let you easily pick her up. Also, just before she went up to roost bar I noticed she would occasionally pant and fluff her feathers. I assumed she was getting ready to lay first egg and feeling uneasy. After I found her dead this morning I checked body: no signs of parasites, no wounds or clear injures, vent looked like this I'm thinking she was egg bound, though hoping more experienced people will chime in. Tried feeling for egg, but didn't feel much (body was starting to get stiff, plus I wasn't too sure about what to look/feel for). Thanks for all input!