Shift in audio track

Hi!

I am editing a video and have somehow managed to put my entire audio track out of sync. I'm not sure what has happened, none of the tracks have moved in the timeline but the audio and video that went smoothly together are now delayed, it seems all the audio tracks have shifted backward by the same amount.

Any idea of what has gone wrong and how to fix it? The program has autosaved in the meantime so I can't go back....

Do the clips have the out-of-sync indicator? (Or are these clips not linked?)