Personally, I use 2 high capacity 6v AGM batteries in series instead of a huge 12v or 2 12v batteries wired in parallel. I use 2 Lifeline GPL-4CT 6v AGM batteries wired in series to get 12v output.
I have the same as donc13, two 6V AGM batteries, though I bought ours back in 2015 at Sam's CLub for about $183 each. They remain in good service today.
Like donc13 says, a pair of 12V batteries will be only as good as the worse one as it brings down the better one. In an emergency situation as you found yourself in, determine which battery is the worse of the two and take it off-line, then try to reawaken the better battery by itself and live with one battery until you can replace both. That will get you through your difficult situation.
My experience with two different pairs of 12V wet acid batteries is that we got only 2 good years, one marginal year, and one problematic year. Our pair of 6V AGM batteries is coming up on 10 good years.
One practice I have been doing for some years now is when not using our PC, I disconnect all the batteries from the house and chassis, charge them until full, then forget about them until it's time to use the motorhome. When it's time to use our PC, I charge the batteries back to full which happens quickly, reconnect, and all is well.
I used to keep the batteries connected and maintained them on occasion but found that to be a lot of work with occasional gaps of forgetfulness.
My earliest years was keeping the rig plugged into 120V with the on-board inverter maintaining the batteries. That was the worst.
I learned every wrong way on battery maintenance.