Sorry, please tell me about vaulted skulls so I can answer your question. A little background: I have had quite a few breeds of chickens, but these Polish were a Mother's Day gift from my daughter -- so I don't know much about them. She ordered them from TSC, and I don't remember (although I can find out) the name of the hatchery they came from. They sent 12, and over the last month, 10 have dropped dead. Look fine one day, dead the next morning. They are indoors, brooder, heat lamp, only chick food, just like I've done a million times. These are the LAST. TWO. I really want them to survive whatever it is, and maybe if they are a pair, we can make more... but who knows???
A vaulted skull is when the skull has a large knot on top, it's what gives them the large crest. It's not just feathers, it's actually the shape of their head. If they get bumped on it they can die very easily, especially in chicks. The reason I was asking is that non-vaulted polish Roos sometimes have crest that looks like a hen's crest. An easy way to tell if their vaulted is to look at their nostrils, if they have a high arched nostril than they are vaulted, if the nostrils lie flush with the beak than they are non vaulted.