Duck limping

[Hgc]

So this morning, I let my ducks out, they roam the backyard through the day, and noticed one was limping. I don't see any apparent injury, is there anything I can do for him now or just wait and watch it? I know there's other posts like this but I did have a few other questions. 1. I know for sure one is a male, but thought at least one other was female, now I'm not sure. Any thoughts? 2. I have a large dog kennel that five of them sleep in, they come in around 7p and go out the next morning around 7. Is it too small for five ducks?