New disks are getting extremely hot

I used to have 2 x 2TB WD reds (WD20EFRX) with my WD MyCloud Mirror (Gen. 1). After several years in used I was about to run out of space. Hence, I upgraded to 2 x 8TB WD reds (WD80EFAX). Changing the disks and extending the volume was not an issue at all.

With the old disk the NAS was averaging at about 40°C. Now with new ones it is at 60°C. On heavy duty, peaks are beyond 65°C and triggering temperature alarms. I already noticed that certain WD80EFAX firmwares leads up a 5-10°C compared to other models. But 20°C seems to be a bit to much. Does anyone has an idea what to so in order to reduce the temperature significantly?

For someone who is facing a similar problem: I placed a USB fan on top of the Mirror and tilted it by 90°. The temperature is back to about 40°C.

Those EFAX Disks are running at 7200RPM which is where your heat is coming from…