SAN DIEGO — The San Diego Padres ran out a lineup Thursday that resembled one of the many off-brand assemblages they put on the field for so many years (decades) of irrelevance. The difference in this instance was they possessed the third-best record in the National League and had a Cy Young contender on the mound. But on a night he was working with his slimmest margin for error, Joe Musgrove had his first bad game of the season. The Philadelphia Phillies scored several games worth of runs against Musgrove in the sixth inning and beat the Padres 6-2 at Petco Park. Until it unraveled quickly wi…