How is your humidity? Ducks need high humidity to hatch..If not they can get stuck that might cause bleeding. Some ducks also don't absorb their yolk sacks before they hatch. It will absorb eventually though just make sure when it does hatch not to let it step on it. If the yolk sack comes all the way out their intestines can get pulled out along with it. I have had this happen to a chicken that stepped on it's yolk sack.