There is no way you are going to get to the bottom of it without some test breeding but dad looks like he has something different going on than just GHI pastel spider. He may not even be pastel, but a similar morph that causes slightly less head blushing, as his head stamp doesn't quite match pastel. GHI should suppress the white coming up the sides in spider, but his is just as strong as a spider without GHI, so maybe whatever it is suppresses GHI to an extent. Those other two are pretty wild looking too with so little black left.