I said this yesterday, I think he is having a hard time that she is more famous and successful than he is. He used to be the IT guy in the industry, and now, not so much. He hasn't had a hit song in a long time, whereas she obviously has.
Here's what an insider said:
"She's stressed about the tour, they've been fighting. It is probably for the best, because she is going to be on tour for forever. Of course this happens all the time, I can't keep track anymore. But for now they are done."
Hopefully they work it out, I always thought they were a cute couple.