WASHINGTON — Concerned by Monday night’s 7-2 loss to the Nationals and by a slump that has caused the Mets’ NL East lead to fall to just a half-game over the Phillies, Jerry Manuel is having a team meeting this afternoon. The Mets just closed the clubhouse at 4:45 p.m. 5:05 P.M. UPDATE: The meeting has now ended, and the Mets are on the field for BP.