Considering how sweet the boys are, I don't think this will ever happen, but I made a preference for it anyways since I was bored.
Corbyn: Careers. Since you both love each other a lot, it make since that you both just broke up because of how busy you were with your careers, you believed the best way is to break up and focus more on your career.
Zach: Trust. He didn't cheat on you, and you didn't cheat on him. But every single time you went out, he was always panicky and accusing you of stuff you would've never done. You didn't break up because of lack of love, it was lack of trust.
Daniel: Love. Let's just say...the spark was there, but now it's gone. You both deserve to happy.
Jonah: Cheat. You both loved playing games with each other, but one of you (your choice) took it a little too far.
Jack: Never there. Whether it's you or him, your relationship is always the last thing on your mind. Why be tied down on a relationship when you're not even gonna try and make it work?