i have had this problem for a while. My bios says that all 3.3+,5.0+, and 12+ are all low. I have not had any problem so far but it worries me. So i bought a new power supply a thermaltake black widow, and the readings are still low, my 3.3+ is at 3.04, the 5+ is at 4.58, and the 12+ is at 11.26. its clearly not the psu. does that mean its the mobo or maybe the cables, since i use some extensions?
More aboutvolatge readings
Check the PSU with a multi meter, it is possible that the BIOS is not reading correctly.