help! composite deck cleaning

I am having problems cleaning CertainTeed composite deck. "boardwalk" is the style. I am using a professional pressure washer Honda 4500 psi. I use a non-toxic Clorox deck cleaner that apply first and us a perpendicular wand about 4-6 inches above the work. What am I missing? The results are terrible, streaks that I can remove after. Are some composite decks just not cleanable? This has been very frustrating.

Thanks very much for any suggestions

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