Which side draws more current?

[BrianG]

If each pack is balanced on the same balancer via Y harness, there should be no difference between each cell once the charge is complete, provided the balancer has time to equalize each cell. Another way to do it would be to charge/balance each pack individually; same result, just would take twice as long.

I too think there is a weak pack so it appears to be discharged further. It could simply be the LVC is set too low and pack1 is on the sharp slope of the downward voltage slope, while pack2 is just reaching the end-of-cycle knee. I would maybe boost the LVC point a tad. 3.2v/cell works fine for me.