Lightbulb Which rump Genetic mutation exactly is this???

Hello all
Just needed advice from the experts that what genetic mutation of rump it exactly is??
The Genetic history is that its the breed from orange rubino red eyes female and orange opaline male.
The other siblings were female of yellow orange n a orange rubino red eyed female

Further info regarding the gender would be an additional help
Thanks!

I didn't find the right solution from the Internet.

reference:
birdsplanet.com/forum/4654156
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