Have my duckings started laying

We have 5 ducklings, hatched at the start of June, which now live on our allotment, though they live as a separate group to the adults. Helpfully, the group consists of only one drake but four ducks. From our early experience of keeping ducks last year, we were not expecting them to start laying for another two months. And then, yesterday morning, beside the pond, I found a smallish, beige coloured duck egg. The adult ducks are locked away in their duckhouse during the night but the ducklings wander free around the site. This is their choice, not mine. They abandoned using their own duckhouse nearly a month ago. Since the egg I found was laid through the night, it seems that one of our ducklings has started laying earlier than expected. There was no small duck egg next to the pond this morning and a quick search of the allotment turned up nothing but with a bit of luck, the duckling in question (I really should stop calling them ducklings as they are now fully grown) will continue to lay.