Trying to think of the issues that you might have. Cold is an obvious one. That depends on how cold they actually get near the middle where the embryo is. That will be a function of the actual temperature and how long they are exposed to that temperature. I'm having trouble getting my head around you getting eggs that early if you are in Indiana. That is barely daylight.
I'm not sure if you are talking ducks or chickens but the principles should be the same. I remember a thread where chicken breeders were talking about winter hatching, they needed to hatch early so their chickens would be a good age for a specific chicken show they were entering. Some said they experienced lower fertility in the males in winter, others didn't. There was also some discussion on lower fertility during molting. Again, some experienced it, some didn't. No one was sure why.
Are you feeding them differently? It's not just about protein, hatching eggs are affected by various nutrients. Professional breeders use a special feed for the breeding flocks to get an edge. On the scale that they hatch a small difference in hatch rate percentage can make a difference in how many chicks they get. On our scale it's usually not noticeable but they do need a balanced diet.
When I was in Northwest Arkansas I collected chicken eggs to hatch in January, sometimes in freezing weather. I was retired so I was home to collect them several times a day. I had some really good hatches and some that were not great. But the same thing could happen if I collected hatching eggs in April or May during really nice weather.
I don't know what your goals are. Why would you want to hatch now? How would a reduced hatch rate affect those goals? I needed to hatch in January/February so I would not run out of meat in early summer. The number of eggs that hatched determined when I needed to start my second incubation. Usually I got enough that I could wait on the nicer weather and often wait on broody hens.