I store my paper in a large black plastic box, with a snap on lid in the darkroom. The paper itself couldn't have been modified by being in the darkroom, because I printed the same day a new box of grade3 came. My darkroom temp usually stays around 70F. I wash my paper under running water in trays ATM, face up for 1.5 hours generally.
Juan, how long did kentmere tell you to leave the paper in the developer for? Ansco is pretty fast working, but I couldn't see developing for less than say 40seconds. Perhaps my developer does need to be modified.