I have four hens and a pullet that arent laying. The hens (auracana, golden comet and partridge rock) are 3 years old and were very good layers. But then they all just stopped laying within a few months of each other, and that was about 6-8 months ago. They all appear healthy, unstressed, there has been no change in feed, and they completed their molt at least a month ago. The pullet was laying 5/week, but just stopped (though her sister is still laying). Any thoughts? Thank you.