Ducks are not chickens. They need a lot more space and will not do well locked in a little coop all day. They love water and mud and turn many nice areas into mucky messes. But, they are worth it if you are willing to let them be the water fowl they are.
1st, get rid off the dead egg. It will only spread bacteria through those cracks.
Also, stop spraying. Too much humidity is way worse than not enough. It also will encourage bacteria to get through those hairline cracks. The baby ends up sticky or too large to zip. Personally, I don’t add...
I had three Hookbill’s hatch ten days ago (my first babies from my pair). I had purchased a marble tower last year and it came with this blow up mat to keep the marbles from rolling away. It looked like a perfect baby pool to me! They have used it for a couple of days now and are loving it...
They look like Blue Mallards to me but that is not a duckling Hoover’s hatchery (who supply Coastal Farms) sells. If they are Mallards, I believe they should each have one of their back toes missing. All domestic Mallards are required by law to have one removed to tell them from wild Mallards.
If you try it, use Khaki drakes and mallard hens. Holderread says in his book that egg laying ability seems to pass from Khaki drakes. This cross would also be sex-linked for the first cross. All the boys would have black like a mallard drake and the girls would have brown and look like...
That sounds like a predator attack to me. Drakes can be mean. They can pull out feathers, pinch, and scratch. One can drown the other. But, what you are describing sounds like your boy had internal bleeding from a predator attack.