Scenes all muted (xmin-xmax)

Hey everyone,

I have the following problem:

I started messing with the scenes in a new track. For little bridges I normally turn down the volume on the kick for scene B and add some effects or filter changes to the other tracks.

Then suddenly something strange happened. I wanted to turn down the volume of the high-hats as well, but when I did, all tracks became muted. I must have pressed some key combination that is unknown to me that caused parameter changes to effect every track instead only the one I have selected.

Can somebody please tell me how to fix that? Much appreciated.