THE FACT ABOUT DOME CLEANING THAT NO ONE IS SUGGESTING

See pics two and a few. I'm now getting ready to refinish the deck once more this summertime. See photo four of recent problem. The blotchy website seem has rather dissipated as a consequence of weathering from snow/rain (I reside in northern Illinois). What did I do Completely wrong past yr? What do you advise I make this happen year? Do I make us