Shading, and the angle at which sunlight hits solar panels are are significant factors. I know several people who have the Victron controller, and they seem to do a good job of monitoring and displaying battery/charge status. Your wire gauge looks good, and I'm assuming there are no bad connections anywhere. So if your panels aren't shaded, and they're within 10 degrees of the sun, I think they're just not putting out what they're rated at putting out. Not surprising considering the type and source of the panels. Sorry
FWIW, we just finished installing six 170 watt Zamp panels on a Newmar Mountain Aire, and the system was putting out 1070 watts at about 3:00 PM, with all the panels tilted toward the sun - two slightly shaded by trees.
Kev