Are you mixing the W&N with the Ultra Fine in the same quilt? Did you pre-shrink the W&N? Warm & Natural is cotton and will shrink when you wash it, like about 3%, resulting in the noticeable puckering craftern1 mentioned. Ultra Fine is polyester and won't shrink at all. This is also why the Ultra Fine slips, because polyester is slippery. If you combine them in the same quilt, you might have an issue.