Is this dirt or the natural finish of my composite deck?

Question

Update: Added two photos of the bottom of the deck

I washed my composite wood deck with:

• 1 gallon of water
• 1 cup vinegar
• 1/4 cup baking soda
• Soft bristle brush

I thought it would remove what looks like dirt on the deck boards (see attached photos)

Now I am starting to think its just the natural look of the board. I'm not sure what brand the previous owners installed.

If its dirt I thought I might need a more aggressive cleaner or some light power washing. I think its been a couple of years since its had some maintenance

wood board close up

wood board

Bottom of deck Screenshot 3

Closeup of deck from the bottom Screenshot 4

Answer 1

Looks like a perfectly normal faux-woodgrain brown composite deck.