Parasitic drain on 12 volt DC electric circuit

"This is a new problem that results in excessive drain over normal dry camping. We were doing fine for a week, the batteries were charging daily as we traveled and the drain by morning was nominal. Suddenly one morning the drain was excessive, so probably a short"

Or maybe was not getting to a full charge daily and finally reached a level where things shut down on low voltage. Takes quite a bit of driving to get a battery to FULL charge.
Art.