Had a new deck installed 4 mos ago on condo. Started getting blackened areas across top rail inside and out and looks like white and green mold or algae. Almost appears to be coming out of cracks and knots.Treated it with bleach solution but keeps spreading and now on rails. The rest of deck is fine, but this one board always feels cool and wet and remains darker than other boards.It just will not dry. Rest of condo owners do not have this problem and all decks were replaced at same time. Could this board have been moldy when placed? Why is it always damp? Need to seal deck soon and wondering if board should be replaced. Thanks for any suggestions.