Hello, yesterday morning I had checked on my flock of 5 chickens and all appeared well and healthy. It was then later that night when I put them to bed I noticed one was showing signs of clear illness. I have lost many chickens for the short amount of time I have kept them (4 years), most for unknown reasons and have become well adept at recognizing when they feel ill. However recently I have noticed some of my chickens have appeared sick for an hour or so and completely got over it, so I did not pay much attention. This morning, the chicken was dead. She had never shown any signs of illness prior except for last night and was a healthy, egg laying, young chicken, just over a year old. There were not external wounds from what I could tell and it is to my amazement as to what brought upon her death. I also had another very young, healthy, egg laying chicken die in February without any previous signs of illness and no explanation for her sudden death. At the time I had brushed it off as a freak accident, however now after this surprising death i'm not so sure. I'd appreciate any help of any ideas as to what could be causing their deaths. To the best of my knowledge i am doing nothing wrong however I can't help but feel it's my fault. I give them plenty of clean water, food, a clean and well ventilated coop, and a large run without access to any poisonous plants. I have contacted every vet within an hour of me but not one is able to do a necropsy on her (I decided not to do it myself because I have no idea what i'm looking for and don't have the proper tools, and if I'm being honest, stomach to handle it). My hens have been laying thin shelled eggs recently despite their calcium filled feed and free choice oyster shells, perhaps that is in some relation. I am looking to expand my flock but am afraid to get more chickens if the likelihood of them dying within their first year of life is high. Thank you for any help you might be able to give.