This past summer we redid the roof of our 1976 home. The sheeting was puzzle pieced together so we took all of the roofing off all the way down to the rafters. We put 5/8 inch OSB down, heavy duty tar paper, and a metal roof. The top of the entire roof is a vent instead of having a separate vent for the bathroom and the stove. I painted the underside of the sheeting with the same brand of exterior primer and paint that was painted a couple of years ago. The underside of all of the exterior eves are growing mold. I went into the attic and checked the underside of the sheets and everything is okay, no mold. I am not sure why the mold is growing on the outside underside of the eves. Do you have some advice? We live in the Pacific Northwest close to Mt. St. Helens.