Sound Low after 'Undo'

Hi,

I accidently cut a huge portion of my video because I had ‘ripple across all tracks’ selected when I cut something from one of the tracks. I realised what I’d done and clicked ‘undo’ which brought everything back again, but now the volume on all cut up pieces has lowered considerably despite everything being set to max volume which was perfect before I made this mistake.

I’ve noticed this happening before but it’s usually been one small piece where I made the error; this time it’s almost half my video.

What is causing this and how do I get the volume back to the loudness it was at before?

Cheers.