Thanks for your reply and sympathy foxy. She was the first hen that I have killed and I was rather upset about having to do it. A blow to the head with a heavy iron bar did the job very well, and I am sure that she did not know anything about it.
My hen was nearly 3 years old and a Warren. She had laid all through the winter..about 20 or more eggs each month. I was wondering if her illness was due to just being worn out. I did notice a slight change in someone's droppings just before she became ill. They were a little green and more solid looking than before. Then they became a puddle each time she went. Her eggs used to be brown but they became almost white just before she died. She even laid 3 days before she died, in spite of being so weak.
I hope to get another 2 hens to keep the remaining hen company, but was waiting to make sure that she is OK.
Perhaps such good layers do not live as long as the others?