Generally a sudden stop in laying is the result of four things...
1. Molting
2. Stress
3. Diet
4. Light Hours
Molting is obvious, it's a natural cycle but it can be brought on by stress or diet changes outside it's natural cycle...
When we talk about stress it covers a whole gambit of things, from their living accommodations, to their nesting box, to their roosting location, to their interactions with the other birds... It can be a result of changes in scenery, changes in daily routines... Basically there are a lot of things that can stress them out, and you have to look around and address them one by one and see if things change... Sometime a small change like putting up curtains in front of the nesting box is all it takes to remove the birds 'stress' and make them feel comfortable and resume laying... Another common quick fix is to simply put in more roosting space, so they have more room to roost and get a better nights sleep to remove stress...
In regards to diet, this is a big one, on a commercial feed only diet offered 24/7 free choice they should lay consistently, if you offer snacks outside that diet and that includes free ranging their dietary balance can be off and it could disturb laying patterns... Also the quality of feed can have an effect, sometimes it's best to switch them over to a known production level feed, I know that a lot of people like this or that vanity brand, but sometimes switching them over to plain jane consistent results feed like Nutrena or Purina layer pellets for a month will help you figure out if it's diet related...
Light hours, should not be a problem in the summer but the chicken needs light to lay about 14-16 hours of light per egg, if they are not getting sufficient light they won't lay...
