Your birds are really stressed. When the hot weather begins, chickens will slow down laying. You should be getting more than 40 eggs per day from 100 hens. The following problems can cause stress:
1. Poor nutrition- What are you feeding your chickens and do they have plenty of feed?
2. Not enough water- Birds should always have fresh water.
3. Crowded conditions. Not good any time of the year.
4. Heat- Do your birds have a place to go and get out of the sun? They need shade and lots of it. They can not be crowded in the shade.
5. Ventilation- Is the coop well ventilated, especially at night. A cheap window fan placed into a window will add or remove air to or from the coop.
6. Disease and parasites: make sure your birds are free of external parasites. Parasites just add to the stress.
My hens egg production has been cut in half due to the heat.
I live in Missouri and it has been hot of late. 95-100 F.
If you can eliminate the stress, it will take about two weeks to get the girls laying again.
If your birds are slow at molting, it may take months to get the egg production back. If the birds are fast molters it will take weeks. Birds that molt during long days (summer) are slow at recovering their egg production. Not good news.
Tim