Can't quite see through all the luminous spaghetti, but does your order go like this:
res>pump>T>rad>cpu>gpu>T>res
with the NB on the T lines, basically in parallel with the rad, cpu and GPU???
If so, I would hazard a firm guess that the NB path is getting more flow than the other path and basically BYPASSING the radiator..!!!
........but if your temps are ok and you are happy with it, then fine.