I'd like to suggest you ease up your expectations, a bit. We get so caught up in the "egg a day" measurement, that we forget they are not machines. There are more than a few reasons why hens slow down or cease laying. Some we know, some are only in the mind of the bird. This is why egg laying has always been measured on an annual basis.
For the record, a 200 egg year has long been considered good. 250, excellent.
All hens naturally go through a slow down at 12 months as part of the molt. There are those rare few that lay right on through it, but the majority simply stop while ther bodies work to replenish reserves and grow new feathers.
It used to be that a pullet became a hen when she reached her molt - it was seen as a pivotal point in her life and she was expected to taper off then.
It is also getting hot out, to be combined with the 12 month mark. Summer heat also affects them by slowing them in general, to include laying. In extreme heat, they may cease laying altogether.
All other things being equal, it is likely a combination of the weather and the molt.
Make sure they are clean and free of damp or muck, well fed and kept them as cool as you can make them. Then let Nature take her course.
