How do I center pan a whole sequence (or in to out points)?

I had something unexpected happen today. I'm editing a 4 act show. I've watched the first 2 acts and when I get to the third, it's much louder. I find that 1&2 are panned center. So I fix it so 1 is panned left and 2 is panned right. Then on a whim, I go back to acts 1&2 and they are both panned center as well. I open the previous save (no one else has touched this project) and everything is panned left and right. Somewhere along the way, all the clips on 1 and 2 got panned center. Somehow I was able to do accidentally what is apparently impossible...adjust the panning of the entire track across all clips through the duration of the sequence. If it can't be done, then it's a bug? And I'm talking about the clip mixer, not the track mixer. I'll not rest until I figure this out but I've looked before for an answer to this. It's easy in Avid but Premiere has no way to do it short of pasting attributes to all clips.

thank you for your reply. I'm actually not a newby at all but for some reason everything just gets panned left -100. The proposed solution worked for me. 

is the audio track mixer set correctly? (Often newbies make adjustments here not realising there are two audio mixers).

Centre pan first clip (using audio clip mixer, not audio track mixer).

Select that clip in timeline & copy.

Select other clips you you want to affect & 'paste attributes' - check 'panner' and click OK

(There are various methods for selecting clips)

The only way to get them that way is on purpose.  Undo what you did.

Try the Audio Mixer