Roosting not laying

[gman mo]

My Three Chickens were going strong till last week. Hot weather may be why, but they have quit laying and don't want to go in coop or run. I let them roam my fenced off garden and now they roost on fences and are not to interested in eating either. Otherwise look healthy. These birds are all over two years old and other than a little broodiness have not been a problem. Stumped.