Do you leave food and water in the coop at night?
I would not worry about the food as much as the water. The ducks will be able to survive 12 hours without a meal. The water I would leave, especially with summer just around the bend. I have the privilege of not having to lock my Muscovies up a night. I do when they are little though, they are a perfect snack for a great horned owl. When they are locked up, I always leave water.
After 3 or 4 weeks of having to clean the coop daily, I removed both water and feed in the coop at night. This has reduced the mess in the coop significantly. I let them all stay out until it's after dark, I'm usually out with them, giving treats or just getting my own therapy. They spend between 8 to 9 hours in the coop at the most and I haven't had any trouble at all. I pulled the plug and went cold turkey on the change. One night there was feed and water and the next night there wasn't. No one complained a bit. :-)
They're happy as clams with no formal complaints sent to management...
Your mileage may vary.