Mikecb7h22aBass

I have 4 d3400 in the trunk. 3 1/0 tofc shca runs from 410a js alternator . The batteries are ran parallel. The first battery sees 12.6v resting then the next 3 are all at 11.52. I'm running 4 ppi 7000.1 2 strapped together and same with the other 2 pushing 4 skar vxf15d4 wired at 4 ohm. Those are all running off battery 4, battery 1 has my viair compressors , lighting ,and toggle panels. Batteries 2 and 3 have no load. Fused in-between all batteries, with grounds from frame on batteries 1 and 4...question is , why are all the batteries not the same voltage, I also see massive voltage drops if I turn the system up, like down to 10v. Can someone draw me out a wire diagram for what I'm running, please. Or are these batteries just done for? I hope not because if they are I might as well just toss 1600 in the John crapper and flushed it down the drain.