We completed the exterior work on our house (NH, zone 6) in the fall of 2014, including the eastern white pine soffit boards. They were coated with Vermont Natural Coatings PolyWhey Exterior Penetrating Wood Stain. After not touching these boards for almost 8 years, the mold/mildew on them seems like a pretty natural occurrence (I’m confident this isn’t a building moisture issue). I’ve sanded a small section and it’s more than just superficial.

We’re going to be doing some exterior re-staining and touchup in the next couple months and would like to work on the soffit boards as well. Does anyone have a recommendation (preferably based on actual experience) for a wood safe product that could minimize or remove this mold/mildew growth?  Ideally it would be a product that could be applied with minimal follow up (ex: not needing to rinse with massive amounts of water).

Keeping in mind that this work will be 20-35′ off the ground, it will be DIY, and we’d like to then re-stain the boards with a clear or semi-transparent product.

Thanks for any insight. I’ve attached photos and here is a link to high res versions: https://drive.google.com/drive/folders/1BA9dvwI8n-gGbkYri9sBd3TtoGphHt8_?usp=sharing