That would surprise me because they are really well fed... A kilo of peas per day has been shared between the 2 flocks (18 ducks) for weeks now to support summer stress and their factory food (half of what they get, the other part is mixed grains) is also reinforced by vitamins and minerals.Could have been or early stages of niacin deficiency.Peas give some niacin but I am not sure anyone has figured out how many peas in a day are giving them the 10 mg they are suppose to get.
Good to hear whatever it was the duckling recovered.
In any case, we're glad she's fine. The previous mobile hospital patient a month or so ago was an adult duck with a sudden hole in her flipper. Sprayed with vet spray, given the same vit-min-peas combination as in this round, was also back to regular behavior in the morning.