[prairieschooner]

Jennifer,
It appears that something is drawing down the Batteries. Since you Shut down the Battery Switches and they still went down there could be something wired direct that is drawing power or simply a bad battery.
Sounded like you used a Hydrometer to test the Batteries, do you also have a Digital Volt Meter?
I would start with a simply approach. Charge the Batteries to a Full Charge with the Shore Battery Charger and then measure the Voltage and Specific Gravity. Physically disconnect and isolate all of the Batteries with the Ground Cables (much safer to keep from arc welding with the wrench). Now wait for a day or two and measure the Voltage and Specific Gravity again, the Voltage would signify a problem while the Hydrometer would describe the problem. Now you should know if the Batteries are in good condition or if something has been wired to bypass the Battery Switches.
If all is well there is a Clamp on DC Amp Meter that could help with trouble shooting a power drain. I want one but haven't had to buy one yet, a friend loaned me his and they are great. Here is a link;
http://www.westmarine.com/webapp/wcs...classNum=10600