um I've never hatched ducks and am fairly new to chickens but quickly learned the hard way that sometimes chickens take longer than the books or whatever says but never by that long. According to what people say here for this bird you have is average 26 days so be my lesson and that day I would say 27-29 days may have a chance so I would give them like 24 hrs- 2days over then help them out BUTTTT don't just go at it like a bat outa **** just start with a very tiny air hole to let some oxygen in and give it a chance to "eat" that yolk. if it still has trouble inch a sliver more. I found this can encourage a weak chick or a chick not getting oxygen at right time (reason I have no idea, God only knows why), and oldly enough it seemed with some of my chicks on pip day they seemed to hatch better in my darn hands than in that incubator, and those turds are healthy 5 month old or older spoiled rotten silke/sizzle chicks who scream bloody-murder when I go somewhere. but anywho, never have I yet seen one go That long as yours did and survive. And no this is not your fault, tho I felt the same at first too, it is partly just mother nature and chicks/ducklings to week to survive, and maybe a bit of incubator not reading right on temp./humidity/whatever. That's why some can take longer to hatch than the 26 days in this case, because not all incubators are set the same (factory setting) and not all work right enough to keep an accurate reading. I would try again and get a thermometer not part of the incubator and use that to guide me in tinkering and adjusting the settings right and if it's a malfunction keep an eye on it. Or I'd just say "man,this is too much for me" and buy ducklings hatched by the pros or those better at it than I,lol.cheer up don't give up be as stubborn as the breed and one day it will be worth it because they do love you back, believe it or not!