Hatching problems

[jbkirk]

So I have a Hovabator and lately I have been having terrible hatches 4 out of 19 (4/9).
This is the position (maybe slightly to the left) of the eggs during the last hatch (12 made it to lockdown)

Red = hatched.
Yellow = mostly developed
green = almost mostly developed
blue= clearly undeveloped

Are there any suggestions?
Edited to add that the ones which hatched were almost directly under the heating element(as was the thermometer, and that all the chicks that went into lockdown were alive, just at different stages of development.

 

[ChickenCanoe]

Have you fumigated/sterilized since previous successful hatches? Have you calibrated thermometers since then?
Breeder nutrition is another thing I'd look at.

 

[jbkirk]

Have you fumigated/sterilized since previous successful hatches? Have you calibrated thermometers since then?
Breeder nutrition is another thing I'd look at.

No and No. Today I moved the thermometer around and it was registering different temps in other locations.

 

[ChickenCanoe]

Is it still air or have a fan?

After several hatches, (preferably between each) it needs to be sterilized.

 

[jbkirk]

Is it still air or have a fan?

After several hatches, (preferably between each) it needs to be sterilized.

It is forced air, which makes the temp differences so strange.
I do use a liner during each hatch which I throw away afterwards.(newspaper)
I also have removed the plastic water trough, would that make a difference?
When I did eggtopsies they just looked underdeveloped, not diseased.

Edited to add that the fan is still working.

 

[FridayYet]

Do you rotate egg position when you candle? What was your humidity day 1-18 and how were the air cells?

 

[jbkirk]

Do you rotate egg position when you candle? What was your humidity day 1-18 and how were the air cells?

I did not.. I did a dry hatch, so about 35-40 %, according to your chart they were almost exactly the right size.

I only candled on the 7th and 18th days during the last hatch to see if that would make a difference, but it didn't.