I don't buy into the whole Ameraucana offspring that aren't color/pattern pure aren't Ameraucana idea.I wondered about that, too. She has the slightest bit of a "painting" of inky grey on the very tops that is hard to see unless you're looking. She's the weirdest one of the 8 I hatched. The only one with no beard and very little muffs by her earlobes. I did help this one hatch and she struggled to thrive for a while, but I doubt that had much to do with all of these things. I think the seller THOUGHT she was selling me "Pure Ameraucana" eggs, but was really selling "Americana" ((shrug))
My issue with yours is that pullets leg color. Yellow skin is incorrect for Ameraucana and for a bird to have yellow skin it had to get that gene from both parents.
Yellow skin is recessive to white skin so since yours are hatchmates the male could be carrying the gene hidden.
That's just a lot of birds from that line with the wrong genes. I'd guess you're right. The breeder probably was unaware her birds weren't pure.