It looks like the fireworks between Katy Perry and John Mayer are over... again! According to US Weekly, multiple sources have confirmed that they have split for a second time. "It's sad, but it's not over until it's over. You have to see how things play out. She's leaving the window open. They have both been so focused on work," one friend revealed. So could this just be another "break"? The couple broke up for the first time in August of 2012, before reconciling a month later. Since her divorce from Russell Brand, the Part of Me singer, 27, was also linked to Florence + the Machine guitarist Robert Ackroyd. Mayer's exes, meanwhile, include Taylor Swift, Jennifer Aniston, Jennifer Love Hewitt and Jessica Simpson.