3rd hatch of the year. now a ???

[pintail_drake2004]

So, my wife and I just hatched our 3rd batch of the year and we have noticed a trend. We use a Hovabator with automatic turner, and have had really great success. Our average hatch rate is running at 85% this year. We noticed that the majority of our chicks hatch on day 19 with consistent heat and humidity. We use to lock down on day 18, but I believe that I could increase my hatch rate if I locked down sooner-seeing as the majority of our eggs hatch early. Would this be advisable to lock down on day 16 or 17?

 

[ChickenCanoe]

That would be advisable. But a better approach would be to lower the temperature. No matter the temp reading on the incubator or your thermometers, you have been running hot throughout. That's what hatching on day 19 tells me. Maintaining the temperature at exactly 99.5 all 21 days should net you an even better hatch rate.
How are you measuring temperature? Types, brands and models of thermometers. Thermometers and incubator readings are notoriously inaccurate.

 

[pintail_drake2004]

The temp holds consistent at ~99.4 to 99.7 using a mercury and a digital thermometer in the incubator on opposite sides. The digital thermometer has a humidity gauge on it too, which we try to keep about 55% give or take a little. It typically spikes in humidity right after I add more water obviously, but levels out quickly. I've been happy with the 91, 77, & 87% hatch rates this year. Should I lower the temp to under 99.4 and stretch the hatch out an extra day?

 

[ChickenCanoe]

You should get an accurate thermometer so you know what the actual temperature is, not the readings that have had eggs hatching on day 19.
I've long recommended these two thermometers as the most accurate I knew that wouldn't break the bank.
https://www.thermoworks.com/RT301WA
https://www.brinsea.com/p-394-spot-check-digital-incubator-thermometer.aspx
I recently found a new one that is extremely accurate and reports to your smart phone by bluetooth.
https://www.amazon.com/Govee-Thermometer-Hygrometer-Bluetooth-Temperature/dp/B07R586J37

 

[Coffeebean1947]

I believe op said they have to different types of thermometers in their incubator for accuracy, one of which is a mercury thermometer.

 

[ChickenCanoe]

I get that but just because someone has different thermometers doesn't mean any are precisely accurate.

When I first built a big cabinet incubator, I had 7 different thermometers. They were all junk.