Cedar Deck Pacific Northwest

1. Northwest Oregon
2. Partial shade, under large Douglas Firs - constantly wet 9 months out of the year.
3. Cedar
4. Mildew issues and surface moss
5. Blackening with mildew, very difficult to remove.

In short, we installed this deck 12 months ago and per some misplaced advice and builder's statement that wood was cured we applied Sherman Williams Super Deck transparent deck stain after a couple of weeks. This winter, the mildew and moss really blackened the deck in areas where debris sat (though the areas under furniture look new).
We are cleaning the deck with Cobot wood cleaner concentrate, which is taking a high concentration and lots of scrubbing to remove the mildew. We would like to get suggestions as to what product we can go back with that would resist the wet weather here, and could be applied ideally over the existing product as is. I'd rather not have to strip the railings and deck anymore than we have to.
Thanks for whatever advice you can give.