I don't have any input on the brand DeckMAX however, there are a few others I know of that are a bit more reasonable in price.

There is a product by RUSTOLEUM called Rock Solid Composite Deck Refresh it retails around $40/ Gallon.

There is also a SIMPLE GREEN brand concentrate that is blue in color for Composite Decks and Vinyl siding Retails around $20

When all else fails you can use TSP and a bit of elbow grease to get the boards looking like new again.

The big thing is to make sure whatever cleaner you use isn't Solvent base- or it will eat away at your boards.

Thanks I will look into the rustoleum product, I can clean the boards with 30 second cleaner which works well but the boards that are in the sun are bleached out and in need of some refreshing. I have spent several weeks in Alaska, unlike anywhere on earth that's for sure.