Seven awesome chicks! But one was DIS... not sure what happened

[Urchickchic]

This is my second incubation, set 9, one was not fertile, 7 hatched, they started on Day 20-22, and are doing great, leaving one that was DIS. Did an eggtopcy today after water candling with no movement.
Fully formed chick, had not absorbed yolk so made it to maybe day 19? Was moving and viable at last candle on day 18 at lockdown. Used a janoel12, this egg was 4 days old from my hens when set. They were dry incubated as the humidity was close to 50% and humidity raised to 65% at lockdown. Temp seemed to drop a degree in my thermometer so I increased it to 39c around day 15. Previous hatch (7 of 7) temp was 38c entire time with more humidity as it was late summer and its humid in MD. Sorry for the long post but wanted to give you all as much info. Just trying to see if there is anything I can avoid in the future. Thanks in advance. I have learned so much from everyone here!

 

[chickengeorgeto]

As a general rule fully formed chicks that dies after day 18 was laid by a hen or maybe fertilized by a rooster that had issues with malnutrition. This means that some of the nutrients in the egg were in short supply resulting in a weakened chick who lacked the vitality to pip and hatch. This is more common when hens have been in production for months at a time with even a "mostly" adequate diet. Mostly just doesn't cut it.

 

[Urchickchic]

The eggs came from my hen and roo which are on unlimited Layer feed, also get treats (mealworms sunflower seeds, leafy stuff from compost) and free range for two hours each evening. As the days have gotten shorter and colder I know there isn’t as much stuff to eat while freeranging —the bugs are in shorter supply, etc. This egg was from our EE who doesn’t lay every day. She started laying in August so perhaps one wasn’t 100%? Or perhaps they should have some other supplement?