This batch was from my own birds. I’ve seen it one other time, but it wasn’t from my birds. It’s my cheapy incubator that most likely causes the issues. In the first week, my incubator fluctuated badly with temps. Then someone mentioned insulation and it has fixed the fluctuation problem. But the damage had already been done.
It looks more like a lack of brain coverage or skull deformity.
I'm sure you're already familiar with vaulted skulls from Silkies but just to be sure, I know some people think there's something wrong with their chicks the first time they see a vaulted skull.