I'd agree. We had much cooler weather for so long and now back into the mid to high 80s. It is also the time of year that they tend to start slowing down and beginning molting, which will halt egg production.How long have yours stopped laying for? I have a couple that are doing the same thing. I think it's the weather. But Im new too.
If it was just one hen, I'd consider egg bound as an option, but the likelihood of all three becoming egg bound at the exact same time would be very very unlikely.