Split charge voltage at rest?

At rest my batteries show about 12.5v, is that OK?

With the ignition on yes, as you get a bit of a voltage drop. If your concerned turn off ignition and test batteries with a meter, you will find the reading a bit higher.

That is with the ignition off.

Look OK to me. I'd expect them to show about 13.5 to 14.0 with the engine running and the level in the pic after about 15 minutes of switch off (maybe quicker, haven't ever put a clock on it).

Thank you!

Can't see the pic but depending on your system, the aux battery will continue to draw from the main battery until voltage set on split charge is met (usually ~12.6v). So if your aux needs charging, your main battery will continue to charge the aux even with the engine off. Your main battery will then show 12.6v at rest. The aux battery wont charge until main battery is over something like 13.5v. Make sure you are testing when everything is fully charged.