Hello - I've had the same mold problems with Trex, it began six months after installing. I've called Trex, submitted a claim, & pictures. I did receive a a "goodwill offer" for settlement of $350 to have it professionally cleaned. Terms of accepting the offer, I'm not supposed to talk about the settlement or say anything negative about Trex; guess I've blown that.
So - It's my understanding this stuff can be painted or stained. If I do will the mold continue to bleed through? Makes me sick to see it.
There is a current lawsuit in CA for mold and mildew issues (black spots). Please contact www.hbsslaw.com
Also, for the flaking and warping issues, Trex acknowledged there was an issue. The link is
http://www.trex.com/legal/Claim_Form.pdf
Keep up the fight, don't let anyone tell you otherwise. I hope this information helps.
As for the painting or staining, I'm waiting to hear about the lawsuit for the mold. Please contact www.hbsslaw.com before doing anything to your deck.
Believe it or not this is not the fault of the composite, but what has gotten on the deck surface. Pollen or any other airborne particles that land on your deck have a tendency to mold and mildew. All composite manufacturers recommend that you clean you deck at least once a year to get this debris off.