After the rest he looks much better. The area around absorbed yolk is dry now.
He pooped dark green and white. His eye was shut at first, because he got a lot of gunk from inside the egg on his head, and it dried up. In the morning, he managed to clean himself up a bit and has both eyes cleared up.
I am a bit worried about his weak legs now. One might be facing a bit outwards so I'll keep an eye on him. He does straighten both legs and both feet seem to be normally developed.
He is not yet interested in water but looks to be snapping at toy's toenails that look kind of delicious to all small ducklings.
I will keep him isolated from the other two ducklings for now, because these two really make a mess in no time. Their bedding is never dry and poo-free only for a minute.
The healthy duckling is very interested into the newest sibling and is not acting aggressive towards him. I introduced them when he jumped out of the brooder like the third or fourth time, trying to get to him. That one sure is a jumper.