3.0V???? your CPU would have blown up by now
I think you mean 1.3V, I would not exceed 1.5v core with that chip otherwise long term use will cause damage.
as for the loop on your GPU's is the primary card (card closest to the CPU) the first in the loop? does it receive cool water from the radiator. or is it last in the loop? if it is last than its temps are going to be around 8C or more hotter than normal.