I completed my 20 x 12 deck last September (2015). I read to let the deck "age for 3-6 months (PT Pine). I let it age for a year (now 2016). I have gone back and replaced all the screws and began sanding the entire deck. My question is should I wash / brighten the deck after sanding? And if so, Do I need to sand it again after the washing/brightening prior to staining?
I would strip and brighten as it looks like you still have some old stain in the wood grain. No need to sand after.