I have 5 hens that are 24 weeks old. They were hatched the last day of March. The Buff I have started to lay 2 weeks ago and was steady but now she has gone broody. I'm gently trying to break her but on to the more important question I have. My other 4 hens are not laying any eggs. The other chickens are 3 Spotted Sussex and an Austrolorp. Not an egg from any of them. They are on layer pellets, get 10% of their diet from treats, they free range for approx 2 hours in the evening, have crushed oyster shell and chicken grit available 24/7. They have 4 nest boxes made to the specifications of a 'How to Raise Chickens' book. They have red waddles and combs, they are very fluffy and feathered and not a sign of lice or mites. They did have a respiratory problem months ago and were on Tylan for a week prescribed by a vet. Please tell me what I am doing wrong.