Really hate to replace it, only two years old. What's weird is it's only the trim around the storage doors. The mildew on the corner trim cleans up fine with soap. The trim that won't clean feels more porous so I guess it's a different material. I was in the middle of washing it when I posted the OP and spoke to soon on the corners.
On a second note, and to just vent for a sec, the frame looks like A** on my two year old camper. Really bummed on how horribly faded the paint is on the entire frame. Going to be painted most of it soon I guess, not happy.