I spoke to a friend, and her idea was maybe the temperature differential caused by the cool bottom of your tank, under the sand, and the heat of your lamps. However that usually causes condensation on the tank bottom. Have you tried putting some foam near the oulet of your skimmer, just to break up the chop? I was thinking of some kind of thick block of foam.
Also, you could get some thin acrylic, and either cut it or mold it to fit around your skimmer and just over the top of that section of the sump. It wouldn't impact the function of the skimmer as long as the venturi isn't blocked.
Finally, I was able to fine a small clip fan to use in my cabinet, which cools the tank. I imagine you could use a little more air to aid with evaporation, so setting up that small fan, but pointing it at the lights, would fix much of the problem.