Reasons why hens slow down or stop laying...
...shortening daylight hours and no supplemental light being provided.
...old birds. After their second laying cycle, some breeds significantly lay less eggs are tend to stop early each year.
...wrong breed. The commercial heavy egg layers are best for production through the year. Other breeds, mixbreeds, and in my case the ferals, lay less and stop early.
...poor diet. Not enough protein or calcium will reduce egg laying. An unbalanced diet will also affect egg laying -- too much if one thing or not enough of another.
...too much scratch being fed.
...not enough clean water.
...a break in food or water availability. Letting the hens run out of each could shut them down.
...a change in diet. Change the food type, or even the brand, can affect some hens. They like consistency.
...change in environment. New waterers. New feeders or bowls. New roosts or change of location. Remodeled coop. New pen location. New roof or the roof being removed.
...new chickens being added to the flock. Or the significant removal of a number of hens from the flock. Flock dynamics change, thus affecting the pecking order.
...illness. Sick birds often don't show signs, other than eating less and stop laying.
...something new outside of the pen. New dog. New neighbors. Heavy equipment being used. Helicopters flying overhead. Drone flying over the pen. Stockade fence removed. Brush and trees removed.
..predator. A nighttime visitor you're not aware of? A dog visiting the pen when you're not home. Rats. Snakes. Owls or hawks checking the pen daily. Skunks. Raccoons. Possums.
...the weather. Severe storms, floods, extreme cold, extreme heat can all affect egg laying.
...they've gone broody.
Perhaps you just bought the hens, and they stopped laying. Yes, they were laying great for the seller, but changing homes is a real shock for the hens. It is not uncommon for them to stop egg laying.
Not all flocks are so sensitive to changes, but if they already under stress or if they are extremely settled in a routine, then changes could result in egg laying issues.