I built a completely pressure treated deck five years ago and stained with
Sikkens. It's on the north side of the house and now is very dirty---some
black spots (mold, I guess) on the rails, etc.

What's the best way to clean this without damaging the wood or stain (the
stain is holding up very well). I've been told pressure washing is too tough
and a no-no with pressure treated. TSP? Some of those deck
cleaner/brightener products?

Thanks.