Hello, I am hoping for some help here. I just recently stained my 15 year old deck made of pressure treated wood. I used the Behr Premium Solid stain which I transitioned to last year. I do this almost every year and know how to clean and prepare the deck for staining and have never had any issues. I decided to stain the deck this past Friday. I did it in dusk into the night because the deck gets full sun which makes it difficult to satin during daytime hours. I will say that the evening was humid in my area. Temperature probably about 85 degrees and high humidity. I used a paint pad for the actual decking and brush to cut-in the sides and for the rails , posts, etc. When I looked at the deck the next morning, I noticed dark Green blotches all over the decking almost resembling algae or mildew. The wood was also somewhat shiny or glazed. They were dry to the touch - not oily. I called Behr who thought the issue might have been surfactant leaching and gave me directions on how to remove the blotching. It did not work. They then asked me to apply a deck brightener / cleaner and still nothing. They also suggested sanding to see of the blotches would come up and nothing has worked. I am frustrated and think I may have been sold a batch of stain - but am not sure. The only other thing they thought it could be was tannin. The solution they could offer was to prime the entire deck and then apply two coats of stain. Do you know how much work that is? My deck is 350 square feet!

So - I am asking if anyone out there has had this issue and what they might have done about it. To save alot of time, My goal is to try and restain without the primer but I'm not optimistic. I wonder what the dark green stuff is?