PS voltages should be within +/- 5% of nominal except the -12V which can be +/- 10% (so I've read). You are getting on the low end of 5%. 12.4 would be 5%. I would be looking for a new PSU and I'd up the wattage. More wattage is ALWAYS good because you stress the components less (this is always the case).
The funny thing is that this PSU is actually overkill for my system. It's an 850W PSU on a system with an AMD FX-8350 and a Radeon R7 370. 650W would be perfect. So in case I get a new one I might get one with less wattage. Anyway could a lower voltage from the 12V rail result in a system crash?