If broody then either give them some fertile eggs to sit on or ignore and let it run it's course. if that's what it is. When they come outside do they have a really huge nasty poop and ruffle their feathers chasing everyone/ that's another way to recognize a broody. just generally in a bad mood. and if you try to stick your hand under them to check for eggs most likely your going to get nipped which I can vouch for as I have 4 girls right now that are broody and sitting on nothing since I take their eggs daily. But boy can they pinch.
Do they have a pool to cool off in? could something be coming around at night or day that is scaring them? doesn't sound like broody to me especially if they aren't going into their house, but if I was you I would be locking them up in that house for their own protection at night, unless your run is like fort knox. Most domesticated ducks are pretty loud but I feel something else is going on with yours for them to be acting like they are. Corn does add extra heat that's why a lot of us give corn in the winter months for night time heating. but I feed corn to my flock year round too, only as treat though not as sole feed. They need a balanced feed first. Their house needs to be well ventilated because ammonia build up from their poop is very unhealthy, but I would be working on getting them use to laying their eggs inside making sure they have nice fluffy bedding and a quiet place to lay. And trying to figure out what is stressing them out so much, What is your drake to duck ratio? and tell us about their sleeping and foraging habits. and neighbors do they have dogs that could be coming around upsetting your ducks?
Glad to hear they are more settled today, I tell you these girls are as hormonal as us women are so no telling what might have been going on, glad to hear they are safely locked up at night too.
