Your art and coloring is gorgeous and so lovely to look at and just enjoy~
That said, I know these are fictional wings, but the feather-order is still out of order/flipped - that top feather should be on the top of the "stack" - noticed the same thing with Stairs!!!
as well, though it's more noticeable here since the feathers are fewer and the lighting/gray color of the shadows make the edges of the feathers clearer.
This explains it better than me -> Bird Wing Tutorial