Hi nice quail. I am not sure of the mutations that happen with corturnix, so not sure how much help I can be, I just got a full white chick from two normal buttons. I posted about it and someone told me that it could be a recessive gene that by a miracle of nature became dominant in that chick. All of its sisters and brothers are normal like mother and father. This may be what has happened in your case too.
i didnt breed these sorry! a lady who lives near me does. i have gotten another 5 silvers off her since these photos were taken (i also ate the tibetian/tux cause it turned out to be a roo and a nasty one at that!)
the first bird is a sandy brown. i have parrots and in their mutations, we would call that a cinnamon. it would also be known as a pied in parrots, thats why i was guessing the tuxedo? i have no idea really, totally new to the mutation side of game birds hahaha.