A)What do you have running?
B)When was the last time you checked the water?
C)Do this for a real check. Leave all the lights on, then when the batteries are dead.
Check the water in both, top off to the marker with distilled new water. Then remove the cables on one, recharge it at 2 amps.
(this may take 24 hours)per battery
While charging leave your charger above the batteries as gasses go down during charging.
Let it sit and do the other the same way. Wear gloves and safety glasses and use the normal safe procedures for this.
Reason for this is to RE-establish the charge in the batteries.
Make sure you wire brush all fittings and clean the cable connections .
You should be good to go.
Good luck