Beautiful!
If that fence on the left is not within another fence that can keep predators out, I would add some metal hardware cloth - at least 2 feet up on the side, and coming out a foot or two from the base to prevent digging under. Some folks put heavy pavers along the outside edge of their fence, some bury fence, just something to prevent digging under. Predators will reach through or under the fence to snatch a duck.
My ducks started laying at 16 weeks, four days - that was the first egg. It took another 8 weeks for everyone to get on board.
Providing a safe home, fresh water, good food with enough Vitamin D and calcium, a balanced diet, decent bedding, healthy temperatures (like how you are getting ready for winter), and they should lay pretty well.
If you think someone isn't laying after another month or so, you can dab a little food coloring on the vent of the one you think is not laying and then check the eggs to see if they are stained - you know that one is laying.
