If it's only been 2-3 hours, they probably just need more time.
Maybe you should divide the brooder with a piece of wire mesh, so you know they cannot hurt each other, and then quit stressing about it. Make sure each one has food, water, a warm place, and some cool area.
I think that was already tried with the hen. There's a thread about it here:
https://www.backyardchickens.com/threads/chicken-with-egg-shell-stuck-in-vent-i-need-help-now.1520500/
Maybe you can give her a deeper container of water, that is just big enough for her to put her head but not body into, and leave it available in her brooder for her to experiment with.
She might just need practice, and since you keep taking away the deeper water she has very few chances to...
Yes, that's the duckling waterer I was thinking of! I wasn't finding any of the places you've previously posted pictures, so I just tried to describe it.
I've seen pictures of special waterers for ducklings: either a plastic jug with a hole cut in the side, or a plastic food-storage container with a hole cut in the lid.
Either one can have deep enough water for the ducklings to submerge their entire head, but they cannot get their whole body in...
On chicks, I can tell by feeling their crop: it's right at the base of the neck in front, very easy to find. If it contains food, I know the bird did eat, even if I was not watching at the time.
I think ducklings have their crop in the same place as chicks, so you could just pick up each one...