The first thing I would look at is just what Janice said see if there is enough seam allowance to let your 2 long center seams out just a bit and still have enough seam space not to fray. If not I would take the center seams out and the small yellow center triangles. I would add 1/4 inch (cut 3/4 inch) wide white strip to each long side of the white fabric petal then cut bigger yellow triangles and re assemble. That will give you 1/4 inch bigger on all side and keep your outer points.
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The seams where I drew the arrows.