I have 5 coats of Interlux spar varnish on my deck and I just noticed that areas that are either covered by the hatch cover webbing and the area overlapped by the hatch covers are a slightly lighter color than the surrounding wood. Yes, the varnish is quality marine varnish and was advertised to have UV filters. The boat is just completed, has maybe 30 hours in the sun. Is this something that I should have expected? If so, just how much discoloring should I expect? I would have expected none, but...