Dead in the Eggs (DIE)

Last year I had what I thought was a lot of dead in the eggs. I used to incubate in the rack and I was thinking that perhaps the fluctuations in temps were too great and this contributed to it. This year I set up a cooler incubator and the temps have been pretty constant between 80 - 84. I did have spike to 85 - 87 degrees a few weeks ago when I added water but that was only for a few hours. I bought new perlite this year and used new containers. I had a clutch that was very small hatch out just fine over 2 months ago. (That was a weird sort of unexpected clutch.)

My "first" clutch for the season starting pipping and hatching at day 67 and so far I have 4 dead in the eggs out of 17 eggs. I am pretty sure another 3 are no good. These look like normal hatchlings and even start to pip but make weak slashes. This is from a female that threw a perfect clutch last year (no DIE) and a first time male. I do have 8 hatchlings that are fine and another 3 or 4 that are pipping that look good so far.

I have another clutch that is day 65 with no pippies yet and three others that are due to hatch over the next month or so.

Does anyone have any experience, thoughts or suggestions?

I don't have much experience, only having one DIE before, but I wish you the best of luck. That sucks that so many didn't make it.