OK update guys, checked with my multimeter it shows 12.xx V at 12V rail so I guess the reading from software is inaccurate.

Here's something else I noticed. When I try to stress my GPU, all looks fine. But when I stress both my GPU and CPU, my PSU making weird chirping noise. Some says it's capacitor problem, anyone experienced this before?

And one more thing when both stress began, the GPU load decreases while CPU was in full load.