Hi,
Speedfan can give wildly inaccurate voltages it reads them from the bios, but sensors are not all, to the same standard,
the only way to test the voltages accuratly is with a muti meter under load from the 12v molex when under load,
What psu have you got , how old is it, some lesser models start going mameries virtical after a few years,
worth a shot if you have a spare one,
cheers