80's teen star Tiffany is still on the road singing her hits ... but her latest show in Florida struck a sour note.
Tiffany was onstage Sunday night in Melbourne, FL with her band, belting out a few tunes including her hugely successful "I Think We're Alone Now."
However, near the end of the song, Tiffany apparently hears or sees something she doesn't like in the crowd ... telling them, "F*** You!!!"
A rep for the singer tells us Tiffany had lost her voice and got frustrated with her performance, though it's not quite clear why Tiffany flipped on concertgoers. She had struggled to hit several notes during the gig, so it's possible they were heckling.