A source tells E! News that the Prism singer's upcoming world tour was a big issue for the former lovebirds. The insider says Perry was definitely putting her work first, however adds that it's unclear whether or not her upcoming tour was the actual final straw for the split.
Perry is booked solid from May until November after recently adding another leg of her tour.
Katy announced on Twitter yesterday that she will be spending November in Australia and New Zealand.
"PERTH, ADELAIDE, MELBOURNE, SYDNEY, BRISBANE! I'll be seeing YOU this November! Stay tuned for MORE info," she wrote, and added, "And don't worry, New Zealand... I'm coming to see you kiwis too! Dates announced soon!"
Mayer is also scheduled for a worldwide tour from April to June.
Regardless, there were a few signs that may have been signaling trouble in paradise for the twosome. Mayer was noticeably absent from Perry's side on her recent trip to London and Milan. She returned home to Los Angeles on Friday, as her former beau remains in New York.
Despite some early ups and down, the musical pair fast became one of Hollywood's hottest couples, sweetly gushing about each other in interviews and collaborating on the song "Who You Love," off of Mayer's latest album, Paradise Valley.
In fact, the duo have been the center of engagement rumors for quite some time now, with the most recent round of are-they-or-aren't-they being sparked by the huge diamond ring Perry was wearing at the Elle Style Awards last week in London.
The two first went public with their off-and-on romance in summer 2012. They split briefly, reconciled, called things off again last March, but then seemed to be going strong once again.
Do you think Katy and John will get back together again? Sound off in the comments!