No need to worry much. It's when the voltage drops way below the output that you need to worry.
Seeing that you didn't give any info on the PSU in question, is it higher than 400W? For as far as I know that's quite normal then.
If it drops to below the 12V, 5V or 3.3V given standards, then it is time to clean your PSU's fans & fan-grills. Dust may have cooked up onto them giving you not enough airflow.
Also, Asus Probe isn't really a good measurement device, no matter if it comes with the Asus motherboards. It told me my environmental temperature was 78 degrees Celsius. That would've cooked me a long time ago.

Please uninstall it, and if you need something a bit better, check out the last version of
Motherboard Monitor.