Master volume clipping, tracks not?

Hi all.

Im using garageband 10.1.1. and i had a question. My master volume is clipping but, my tracks aren't. What would cause this and how can i fix it?

Im using real instruments (guitar and bass) and using 2 tracks for drums (one track kick and snare, second track cymbals) and one strings keyboard sound.

I lowered the volume and eq all the tracks so they are barely going into the "yellows" about half the song. Like i mentioned, they are barely going into yellow so no tracks are close to clipping into the red. so, since i'm pretty new at this, i know i must be missing something and i notice that the master volume only clips when more that 2 tracks are played at once.

Lowering the master volume so the tracks won't clip takes alot, -7db to be exact.

any ideas?