Brett Oberholtzer and Jarred Cosart weren’t part of the Astros’ starting rotation when the season began. Brad Peacock was, but he only recently rejoined the unit after losing his initial spot and making two trips to Class AAA Oklahoma City. With three promising young starting pitchers needing innings during the final two months of the season, 34-year-old lefthander Erik Bedard still contributing and a porous bullpen regularly giving up game-changing runs — as in Wednesday night’s 7-5 loss to the Red Sox — the Astros made another unconventional move Wednesday by deciding to employ a six-man rotation. After hinting at the move toward the end of a recent 10-game road [...]