Did you use any antibiotics or Blu-kote on the bill? I have a duck that was just attacked and has a hole and crack down the top of her bill about 6 mm below her left nostril. the hole through her bill is about 3 mm the crack about 2 centimeters. The crack doesn't go through the edge of her bill...
I recently had 7 runners hatch. The first hatchling was falling behind in weight, and would just peck at the others and started separating from them... wasn't eating (starter crumble) or drinking. I took a hard boiled egg and a large pinch of nutritional yeast and whizzed it up in the food...
I've been a long time lurker, and have finally decided to take the plunge back into Poultry Culture.
I do have 'intermediate' experience with animal husbandry, having lived & grown up on my G-Ma & G-Pa's cattle ranch in northern California. Back in the day we had a little bit of everything...