I'm a little confused over the day 19 hatch comment. If set on the 18th they shouldn't be scheduled to hatch until the 15th.
Forced air or still air incubation?
Duck eggs tend to be more fragile and react worse to shipping trauma than chicken eggs.
Where the eggs overly dirty or had they been washed? Either one of the two can have an effect.
I think you can expect a ton of questions before this gets narrowed down.
TX is right about the variables. So many things can go wrong.