Batteries Slowwwly discharging

I have a Multiplus II x120 24V with 4 200AH 12V batteries. The multipuli is in the “On” position.
I am getting shore power on both legs. The battery percent is slowly dropping. Over 14 days, I’m at 95%. Any reason this is happening? Over the winter they always stayed at 100%

Is the voltage dropping though?
What are you using to measure SOC?