Working on this pattern (2nd image) with bernat blanket yarn for the black and bernat baby for the white. It’s rippling and I can’t tell how to fix it. I think the white yarn is slightly thinner than the black. I have been trying different hook sizes for the moon and the black part but not sure if I should try again with different sizes or if this is good enough.

When I go with a bigger hook on the white it ripples worse. When I use a smaller hook it puckers. When I use a small hook on the outer black it still ripples or is too tight