I also have Welsh harlequins. They are a beautiful breed. Mine are 26 weeks old. Two of them started laying almost a month ago, but two have not started yet. I'm hoping they will start before the winter sets in, but I may be waiting until late winter or spring to see more eggs. The two that lay now lay two eggs every single day, together in one "nest" in the straw inside their house. The nest moves to a different corner of their house every few days.
Ducks typically prefer to be close to the ground and are known for not being particularly interested in nesting boxes. My duck house is elevated four inches above my duck pen and has a shallow ramp from house to pen. My ducks willingly go inside most evenings and I close their door, which is a drawbridge style and becomes their ramp when down. We have too many potential predators to leave them in the pen at night. The pen is pretty secure, but the house is even more so and is insulated against the winter cold.
How much higher than the ground level is the upstairs part of your coop? How steep is the ramp? Ducks have different needs and preferences from chickens, since they don't perch and their feet can't grasp onto things the way a chicken's feet can. Mine clearly feel safer in their house at night, since they are often in there waiting for me to close their door when I go out to secure them for the night, but others here have mentioned that their ducks like to sleep outside in the run instead of the duck house. My ducks lay sometime overnight, as the eggs are always in the duck house. Sometimes, the ducks bury their eggs in the straw and I have to look for them.
Maybe someone else here will have some ideas for you. You might want to post some pictures of your coop so that people can see your set up and possibly offer better advice.
