Inverter charger RC7 GS

[Outbound]

Not sure why my house batteries are only charging to 12.6 volts, my RC7 panel shows full charge & float status. My problem is my Echo charging will not turn on to charge chassis batteries until house batts reach 13.0 volts, all was working the last time I checked approx. 2 weeks ago. I checked charge output at RC7 panel and it shows floating between + 0 to 2 amps, could I have a bad house battery, house has (4) Golf Cart 6V deep cell batteries, Chassis (2) 12V.
I checked volts at batteries and it reads same as RC7 GS panel.

[vito.a]

When you check the water level and terminals, also check to see if one battery is hotter than the others.

[Outbound]

I will check water levels and terminals. Thanks vito.a