Hi Becky.
From my own experience of a number of coops, and from using a Green Frog myself for svarla years now, there nothing intrinsically wrong with G.F. Nestboxes. They're the right height, ie lower than the perches, and a comfortable size. My birds use them happily. However, I think the problems you're having wi thhens laying away are more likely due to management in other ways. And, of course, as you say, egg production does naturally go down anyway once the birds get older after their first laying season, and also get so much less light and have to deal with the demands of moulting as well.
Laying in other hidden places is of course natural for hens, and I expect it's also a learned behaviour, once one starts doing it the others copy, if they get the chance. So probably you have one adventurous individual who has shown the others how to do it, rather like the way they teach each other egg eating if one gets the habit. I expect they would use the nestboxes in the usual way if they were confined to a secure run. I would also be concerned about the danger to your flock from predators such as foxes, which are everywhere nowadays and if the hens can get out of your garden, it would be no trouble for a fox to get in and pick them off. We've had several sad stories in here of devastating damage from foxes, who kill or badly injure all the flock at one go, they don't just pick off one bird. So, from the point of view of their safety as well as their re-education into using nestboxes, it will be good once you can get that run made secure for them. I expect the neighbours may be quite glad as we'll, as hens can do a lot of damage to a garden.
The other aspect is that I wonder what happens inside the coop during the week, in between cleaning it out with a pressure washer? I find that if I put a good layer of absorbent bedding in the base of my Green Frog, such as Aubiose, or several layers of newspaper, it only takes a couple of minutes per day to remove the overnight droppings and add them to the compost heap. In winter when the birds are in there for 15+ hours, there's a lot of poo but it's very easy to remove by scooping into a bucket, and this keeps the coop clean and fresh without the need for regular or frequent pressure washing, especially in winter, and is much less trouble as well. When necessary (not very often) I spray the inside of the empty coop with Poultry Shield and then just wash it down with a bucket of hot water, dry it off with an old towel, and then sprinkle Redmite powder before replacing clean bedding. I just wonder whether your birds don't actually like the pressure washing, it is noisy and scary, and may make the surrounding area wet and muddy as well. If you do leave the poo to pile up for more than a day, it will cause ammonia fumes which are unpleasant for the birds overnight, and may put them off going in there during the day.
