you don’t want to assist as soon as you see pip they need time to absorb yolks are these your personal eggs or are you buying them from somewhere
I had 7 of my own and another 60+ from a supplier. Bad hatching rate with both - 63% overall for all eggs that went to Lockdown.
my guess would be that it is related to breeder age, genetics and health (ie nutrition)...egg storage and age can be a factor, but incubation temp and humidity can also be a factor. (incubators can malfunction at any time without warning). my “homegrown” eggs have a high fertility rate but tend to produce much smaller chicks with higher rate of issue in direct comparison to myshire eggs, but at same time, I have incubated hundreds of myshire eggs compared to 60+/-homegrown.
I would recommend double checking incubator calibration and possibly running some test batches from each breeding group to start ruling out possible issues. I don’t recommend routine assisted hatching as those that can’t hatch normally tend to have other issues/deformities.
You may be right about age.. as all the 'parents' have just started laying eggs 2 weeks prior to collection.
I am pretty certain the incubators are OK, as I clean and test them after every hatch.
In regards of assisting I was planning to just help them zipping, as they failed at that point.
My next batch is only my own eggs so I will see what happens.