Have 5 hens, 4 RIR's, and one EE. About 8 months, all laying(3-5 eggs per day). Let them out yesterday afternoon to free range in backyard. 5 mins later my son runs up with Penny-crying says he found her just laying in the flower bed. I examined her and found no visible signs of anything. We were all in backyard-no predator, unless it was a snake-but no evidence. Only other possibility was red berries(from a coral/Christmas berry plant) were in the yard. Not sure if poison or not. The other hens are fine. Any ideas?