We had a chicken who kept making nests and wouldn't eat much and she finally passed away. We had heard that sometimes chickens go broody and starve themselves so since our remaining hen was healthy we figured that is what happened.We only had 2 chickens so we didn't want the remaining one to get lonely so we bought 2 7 month old pullets. They were healthy looking and laying daily for about a month and now the one is acting lethargic and laying shelless eggs.She also has runny poop. The original chicken and the other new one seem fine. I don't know why she is getting sick??? We keep our coop really clean, feed a good layer food,let them graze outside for a while each day and give them plenty of fresh water. I am really worried the new chicken might die too.What should I do???