When you installed your avionics, the G3X requires you to do a calibration with the plane in a straight and level attitude... did you do the same thing for the G5? They dont share that info - you have to calibrate each individually.
The pitch offset is limited. The best thing to do is to calibrate both units while straight and level.
I had this issue on my G3X Touch and G5; doing the proper calibration fixed the issue.
in addition to the calibration, there is a manual offset for pitch indication. I just don't remember where it is in the menu structure. Look at the manual. The calibration just puts an offset in there, so it's easier to just manipulate that field.
The pitch offset is limited. The best thing to do is to calibrate both units while straight and level.
I had this issue on my G3X Touch and G5; doing the proper calibration fixed the issue.