Does anyone know what the cause of dull pin-head spots that have developed in my finish after a month? I have a number of bowls I've seen this on, most notably on the walnut ones. The finish is Watco, followed by buffing on a wheel with Carnuba wax. I noticed these small dull spots appear after a month on the inside of the bowls, but not on the outside (or downward facing sides). They gathered dust, but no moisture, during this time. Looking for understanding of the cause, and how to avoid. Thanks!