I agree that the last two need more time to moult out to see what you have for sure. How many other pullets do you have in addition to these three? What about the males, are they feathering in normally?
---------------------------------------------------------------------------------------
I corrected the internal link, so there is a bit more discussion about the silvers, but it seems about like similar suppositions in the more current link. It one of the discussions a bird was grown out and never produced eggs.
Harry, it could be the result of Mosaics like was mentioned or some sparse version of the (Pg+Ml+Co) genes as you mentioned.
Andrew, are you feeding anything unusual (hormones) by chance at this time? I would just put this one aside and see how the others feather in for now.