I doubt batteries are OK. What makes you think they are OK? Also, unless you take the time to FULLY charge them, they will not hold a charge. You need to post MORE info. There is NOTHING that will drain 2 good batteries overnight, even the headlamps being left on.
1. HOW and how long have you recharged the batteries?
2. Are the batteries the original batteries?
3. ONE bad battery will drain the other battery in a bank
4. Regardless if you have 1 bad battery you ALWAYS replace all batteries in a bank at the same time.
5. HOW did you check/determine the batteries were good? Doug