Credit: Larry Busacca/Getty Images Photo: Katy Perry and John Mayer at the Sony Music Entertainment Post-Grammy Reception at The Palm in Los Angeles, California on January 26, 2014

Since Katy Perry and John Mayer called off their relationship earlier this week — and a moving truck was spotted outside Katy’s house — we’ve been wondering why. It seemed like everything was going so well! What’s up with the abrupt end?

According to what sources close to the “Dark Horse” singer have told Hollywood Life, it could be about the big M word: Marriage. Sounds like (amid all the engagement rumors that have been swirling around the couple recently) John’s decided he’s all in, and Katy’s just not. She decided it was too soon to “take the plunge” because she was still afraid a second marriage would fail after her first with Russell Brand didn’t end so well. But can you blame her?

Meanwhile, the source insists that “everything about [John] wasn’t healthy,” and that her friends are glad they’re going their separate ways, because he made Katy into someone who’s nothing like the girl they know.

“[Katy] was not herself when she was with him,” the source said. “She became a total homebody … [She didn’t want to] have fun with her girlfriends.”

However, this might not be the end — after all, John and Katy have split up before only to reunite later. But it does sound like her friends are hoping that this isn’t the case, since they don’t think he’s the best match for her.

“No one would be surprised if they got back together,” the source added. “They love each other and John can be very convincing.”

Source: Hollywood Life