My psu fan is only running at around 1300 rpm and according to asus probe, this is borderlined. Is this a normal fan speed? Is there a way I may be able to adjust this or is this just a fan going out?

Enermax EG465P-VE
+3.3V = 38A
+5V = 44A
+12V = 20A

From a review of the PSU
"This power supply has a lot of fan features. One of the features included is the Teperature controlled fan, also known as "Noise killer". This fan automatically adjusts as need. When your computer case and power supply get's hot, it will automatically speed up the R.P.M of the fan."
A slow speed appears to be by design. If your PC heats up the fan will speed up. If your temps are ok I would ignore the ASUS probe warning.

I used to have a signature but it disappeared and I just couldn't be bothered writing another so please feel free to ingore this.

Lower the PC Probe fan setting so that you don't get the warning