Odd coloration on seedling leaf.

I have a seedling that hasn’t bloomed, just a bud, 'Queen Elizabeth X Neptune. The bottom set of three leaves is yellow but the tips and edges going back are dark green. It looks like the green 1/4" edges are quilted on, seam and all. I havn’t found an obvious cause, can anyone tell me what it is? The rest of the leaves on the plant are normal green color. Thanks, Robyn