Katy Perry and John Mayer have reportedly called it quits, again. The on-again, off-again couple recently broke up just as Katy was preparing for her Prismatic world tour. A source told Us Weekly, "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." Katy and John first called off their romance in August 2012, just a few months after going public with their new love. The two quickly rekindled their romance but parted ways again in March 2013. However, they were back together again by that Summer. The two even recorded a romantic duet, "Who You Love," which they released in December.