I have five 2.5 year old hens (Buffs, a RIR mutt, Wellsummer, Polish banty) four 7 month old hens (2 Aracuanas, Brahma, Barred rock), one rooster (Aracuana) , and they are all free-ranging during the day, coop at night. All but my 2 Buffs have stopped laying. They tapered off to zero about 8 weeks ago - except for the Buffs, who are the heaviest of the gals. They are healthy, not molting, no feather loss, not fighting, they are active and spend most days out of the coop. I have searched our 1.5 acres and watched them, they aren't laying out of sight. The eggs produced by the Buffs are just fine, and they all eat the same stuff. We give them 'balanced nutrition' scratch, which they only eat when nothing else is available because they are spoiled, so we mix it in with the tasty stuff so they have to eat some. They don't like the scratch with oyster shell, and even when they do eat the scratch they leave the oyster shell ( or we crush up their own eggshells, and they avoid those too.) Every day we give them corn, peas, (unsalted) raw sunflower seeds, brown rice, and supplement with other things like melon, papaya, tomatoes, grapes, blueberries, leafy greens, etc. They eat better than I do. We've been feeding the adults the same for 2 years and they've all laid regularly until this summer. It got pretty hot for a while, so we figured that was why they stopped. But then it cooled, and they didn't start up again. In April we got the new chicks, and they keep to themselves unless feeding from a mutual spot. We house them separately with a common fence between coops so they see and hear each other. Although they are full grown and a couple are bigger than the older gals, they are still lowest on the pecking order. They are 7 months old, fat and healthy, but no sign of laying yet. Would having these new girls somehow interrupt laying? I'm doubtful, but anything is possible. The rooster protects and watches over them all, laying or no. Also, during the heat of the summer, we had an outbreak of stick-tight fleas, thanks to the squirrels and rats who raid the coop. We got rid of the fleas using vaseline on the hens, and diatomaceous earth in the coop, and encouraged our dogs to catch more rats and squirrels. The dogs watch over the hens, who are totally accustomed to them. (Don't worry, dog lovers, our dogs sleep on sofas and our beds, too, and live inside more than out, they are spoiled too.) We still have rodents, but managed to get rid of some of the rats. I have friends who suffer more rats and squirrels than we do, and their hens are still laying. We are stymied. Any suggestions?