The Mets were completely shut down by the Astros and fell to a ninth-inning homer by Jason Castro(?!?!) The Mets struggled to notch clutch hits and score runs in Sunday’s loss to the Marlins. They did the same thing in last night’s loss to the Astros. And lo and behold, they looked even worse this afternoon than they did in either of those two games. Today they at least had the excuse of facing off against an ace pitcher, but nevertheless, it’s about as helpless as the offense has looked in any three-game stretch this year. Unsurprisingly, it also marks…