I don't know what age he is or what breed but he is in a (spacious) plastic box I don't keep him under a lamp and there is hay in there box he doesn't seem to have trouble breathing his beak is more red now and I feed him regularly with pellets and water or vegetables. I searched up also that...
I have a male duckling and it seems that he's not as energetic as my other female duckling. He sleeps a lot and won't walk around his box like my other duckling sometimes he just sits there and shivers ,his beak is turning purple and blue and his feet are going red. I don't know if that's normal...