At only 12.0 volts, those batteries are at 50% discharged. The coach batteries I assume are deep cycle which can handle being discharged to that state, as long as they aren't left like that very long. The chassis batteries will not take very many discharges like that before they fail.
Your solar panels are either not working or doing the proper job. Panels should be equipped with a diode which prevent power to back feed to the panels.
How many watts are your panels? What part of the country is the coach in?
If you are in the north with many cloudy days and/or they get covered with snow, the solar during storage may not be an option, unless you add more panels to quickly charge on sunny days. It just depends.
You should definitley have everything shut off in the coach during storage. Most battery diconnects do not shut off the propane and co2 detectors, which will drain the coach batteries if not kept on some sort of charger.
Never owned a DP, so don't know how much hassle it is to 'reset electronics', I can tell you if the chassis batteries are not disconnected, they will shortly go dead without a supplemental charge.
Depending on all the afformentioned, you might be better off to remove the batteries and keep them on a trickle charger at home.
John & Clare - Buck & Zeus - Jack & Husky
2008 Fleetwood Bounder 38P
Towd: 2 HD Streetglides