Hey BJ: Here's a site with several ideas. Give one or all a go and see what you think.
My husband pressure washes ours, but is careful not to be hard on the deck so as not to damage it.
hydrogen peroxide & baking soda are not so toxic as chemicals; cleaner/bleaches out stains along with good deck brush on pole/stick , water to rinse well, soak all plants/ground around the area before and after so it doesn't destroy them and the soil microbes.
Here are some solutions https://www.pinterest.com/pin/101542166584533102/
baking soda and borax should help.