Sounds like you need to check out your charging system. After a few hours at rest, test the batteries directly at their posts with a voltmeter. A charged battery will read 12.7v. A battery is considered 50% charged at 11.9v. Lower than that and it is likely damaged if it won't hold a charge. Then start the engine and take second readings at all battery terminals. You should see a rise in voltage, 13.4v or more, even if fully charged.
Then shut down engines and plug into shore power. Your converter/charger should also charge all batteries and show 13.4v or higher. Be sure to wait a minute or more to test, your system likely has a time delay before connecting all batteries when charging.
If some or none of the batteries show charge, then I'd next remove, clean, and re-connect all battery and ground connections. Again take readings as above, if things now work, breathe a sigh of relief and go on your trip. If things didn't change, you likely have either a bad connection or a failing battery disconnect solenoid.