Think about it for a minute.
If you mute your guitar bus, how do your guitar tracks make it onto the stereo mixdown?
Answer is: they can't, so you don't mute the buss and you don't mute the tracks.
This is assuming that you have routed the output of the 3 tracks to your guitar buss and NOT by way of a send
Track Outputs > Busses
Sends > Busses
Buss Outputs > Master Buss
Master Buss > Main Outs