How to clean mold from a stained and sealed deck?

We have a fairly new deck, treated pine.  Waited 6 months before having it stained and sealed which was this last spring.  The contractor cleaned the deck with a non bleach brightener and used Sherwin Williams Superdeck, oil-based semi-transparent stain.  In the last 6 weeks we have had a lot of rain and sticky aphid droppings from the above trees.  Now we have lots of mold and a sticky deck.  I lightly power washed it a couple of weeks ago, and it looked good that day.  The next day the stickiness was back and with more rain, now it's even worse.  I think I'm going to have to hire someone since I am a female and not sure I can handle the job.  It's a very large deck and I just am not sure what to use and wondering if it needs to be cleaned and re-sealed?  I've read that OxiClean is good to use diluted with a stiff deck brush.  Any advice would be appreciated . . . .