Hi
My last hatch took twenty days. I have heard that jumbos can take a day or two longer than normal sized birds. In my case, I think it was my new incubator. I've only used it for one hatch. Has factory setting for heat but could be low. I tend to be a helper when it comes to hatches. After an internal pip you might try drilling tiny hole in fat side air cell. that would keep them from running out of air before they externally pip. After a day or so I enlarge it enough to see if they are sticky (too wet) or are shrink wrapped(too dry). I also try to see if they are malpositioned. If they are dry I wet tip of q-tip with vetericyn or warm water and moisten membrane. If the veins look pale and shriveled empty of blood I will go ahead and slowly chip them out.
Have your eggs internally pipped? You can tell if they have by holding them up to your ear, do you hear clicking or peeps? If you hear clicking they have broken through the internal membrane and the clicking is actually them breathing air. They should have enough air in a normal sized air cell for a good twenty four hours.