Not even with other ducklings? I would try putting them back together after he/she can walk. For now though, just put it in a separate setup with some blankets and just keep an eye on him/her. You can add a mirror too, as long as it cant get broken. Keep us updated!
Hens go broody when you don’t want them to… and won’t go broody when you do.
Do you plan on putting the duckling with the other ducklings? Just wondering- I have raised ducks with chickens as well and they do just fine!!