Duck Eggs Not Hatching

I have three duck eggs that are now 30 days into the hatch cycle. I have them in a glass aquarium that I have set up as a brooder. It has a warming light and is holding around 98 degrees, with humidity high enough that the glass is mildly fogged with condensation. (I read that higher humidity is good for duck eggs at the end of the incubation period). The eggs have been in the brooder since day 28. Perhaps my delay in moving them out of the incubator caused the delay in the hatch?

This is my first time hatching duck eggs, and I will admit that there were some temperature fluctuations during the incubation. Beyond that, I kept the water runnels full and have seen good development while candling, so I have no reason to think that it is a humidity issue.

The eggs are moving, and when candled they clearly contain a duckling. There is some minor movement inside the eggs when candled.

They have not pipped, but they are rocking. They were sold as Khaki Campbell ducklings, however two of the eggs are blue and larger than the third. From the markings on them, I'm going to speculate that two are Indian Runner crossed with Rouen. The single white egg appears to be Khaki Campbell and Rouen.

I have read that Indian Runner eggs can take up to thirty-one days to hatch, and often hatch around day 30 even without complications.

Is it too early to be concerned? Should I pip the eggs for the ducklings, or give them another day? I suspect even if they do not hatch I will have to crack the eggs and inspect the dead ducklings. For this reason I am wondering if i shouldn't try to help before the ducklings die in the shell.

Suggestions welcomed!