At first glance, perhaps. His homerun total is only at three, and he has just 12 extra-base hits. His batting line in 44 games at Double-A last year was .317/.370/.539. Is he really not adjusting to the higher level of competition?
A closer look reveals that he may be adjusting, only that luck isn't helping. His career line drive rate before Scranton was 17.5% per level (not weighting by PA). His LD rate at Scranton is 20%. The problem is that his BABIP is abnormally low. Pre-Scranton, his balls in play fell for hits at a .344 clip; now it's only happening at a .260 clip. He's also walking slightly more often than in the past.
Back to the 'struggling' side: there are a couple peripherals that show he is still adjusting to Triple-A. He's hitting more grounders (49%) than at any previous time, which is part of the reason he's on pace to set a career high in GDP's. (He's currently at 11. His career high is 16.) He's also striking out at a slightly higher clip than normal.
Just when it looked like he might go on a tear after a 3-5 performance a few days ago, he followed with consecutive 0-3's. However, over his last 10 games, while his BA is only .242, his OBP and SLG are at .375 and .455, respectively. His BB/K rate is also excellent at 7:8. Hopefully we'll look back at his benching on May 7th (after not running out a grounder) as the turning point in his season.
His defense has been about what we could have expected. His caught stealing rate (24%) is virtually identical to his career average, as is his passed ball rate (1 per 6 games) and fielding percentage (.991).
He's still one of the youngest players in Triple-A, so even if he doesn't improve much, it's no reason to panic.