@michaelr123
No, what I meant is:
your As are 10 and 12, while your Bs are 11 and 13, so I assumed A and B are your X and Y, that was in conflict with your M584 where Xs are 11 and 12 while Ys are 10 and 13.
But that's more a naming problem: maybe you named them based on the side of the printer, so X is A2B1 and Y is A1B2 in a cross configuration.
As for synchronization: you need to unscrew the pulley's set screws, move a bit the belts and then screw them again (I think, IIRC).