not laying.

What kind of hens do you have Walfre and how many?  If they are hybrid layers and are 3 years old, that could be it.  Hybrids are bred to lay every day, but egg production drops off in year 2 and can stop completely by year 3.

It doesn't sound like you are doing anything wrong at all.  Good housing, good feed and not too many treats, plus the set-up is being kept clean.  I assume you worm them regularly, but if not, that would be the only thing to add to your routine 

This is the time of year mature hens typically start to molt and laying can slow down or stop during that period as well.  If they are recovering from a mite infestation and generating new feathers for the molt, the nutrition they have may be utilized for these functions instead of laying....no amount of increasing nutrition beyond a balanced diet seems to make a hen start laying again or speed up the molt, though lack of proper, balanced nutrition can slow both of these.

The body can only utilize or process so many nutrients before the excess are merely excreted, so increasing supplements beyond a balanced diet seems to have no true effect, though fermenting of the feed can increase available, digestible nutrients in the balanced ration by changing their form into something that can be better utilized on a cellular level and is the only thing I've seen that will speed up feather replacement and getting back to normal lay. 

Hormones change for molt and that is one thing that attributes to decreased laying. 

Not laying anywhere else, none getting eaten, not been laying for a year now not just over winter. That made them 18months to 2years old when they stopped. One trooper though has kept laying almost daily even through the winter.

Well mine stopped today. Opened up the coop to a nest box with only sawdust and poo . This is the first time we had a blank since they started laying for 15 months ago. They are shedding feathers all over the place but still look good, so I guess they are in their first moult. Sandy does not lay anymore as she was producing soft and no shell, so I am grateful for that, but the other two were giving us a egg every day

I would be happy if we get another 15 months out of them before they stop, but having said that, if we don't then we just have three pet hens, to have a laugh at and look after