The Ivory-looking one could be Pastel or Super Pastel Super Fire and that's how the eyes got to be blue. Another possibility is it's Champagne + something. Enough morphs stacked with Champagne can give almost white animals sometimes.

You can have a dual sired clutch from different years, it's rare but it happens.

The headstamp, are you talking about the third pic and top left in 5th pic? That's pretty common in YB and YB combos.

If mom was a rescue, she very well have YB and you just had goofy odds before.