Left main XLR out is MUCH quieter than right main XLR out???

I have two PA speakers, both the same kind, both with same volume, bass, treble settings on the backs of them, both set to line level input on the backs of them. One of these PA speakers goes out the right main XLR out, and the other speaker goes out the left main XLR out. I have one chael setup for beatboxing through a dynamic mic, and another chael setup for a banjo, which comes in through a DI box. Both chaels have their own specific EQ, compression, and gain settings, and neither chaels are going through the Auxes. They are not stereo linked. When I pan either of these individual chaels fully to the left, they both sound very quiet coming out that left PA speaker. When I pan either chael fully to the right, they sound plenty loud coming out that right speaker.

So I'm stumped. Why does it seem like the output is coming out so much louder through the right main XLR out? Is there a global pan control that I'm not seeing?

As far as I know, there's nothing wrong with that left PA speaker. That left speaker also has some electronic drums directly inputed into the back of it, not going through the mixer, and these drums sound plenty loud through this left speaker. And the signal from the mixer is significantly quieter coming out the left speaker than the right, whether or not the electronic drums are plugged into the back of it.

Please help! This is really tanking my flow.