Why Starlin Castro is having a year off

Starlin Castro has been really awful this year. He has a slash line of .243/.280/.351 and has been struggling since signing an extension with the Cubs in August of last year. His BB% is 3.7 which is absolutely unacceptable and if you take away the HBP his OBP is .271 which is a lot worse. But lets dive deeper. His BABIP is .285 and the average is .300 so he has been a bit unlucky. He also has been striking out a lot more with a total of 72 on the year. The most likely problem is that the Cubs changed his stance to drive the ball more but it is causing him to swing through a lot more pitches as well. He has a noticeable hitch in his swing that is causing him to move around more before the pitch. Another big issue is that he is not hitting as many line drives and is merely grounding out/flying out. The second half is very big for Castro.