Replacement Drive iCloud EX4

I have a RAID 5 setup with 4x 6TB drives labeled:

WD Red 6TB NAS Hard Drive - 5400 RPM Class, SATA 6 Gb/s, 64 MB Cache, 3.5" - WD60EFRX. One of the drives has failed

A replacement drive with the same spec is not available for over a week, but a similar drive running 7200 RPM can be here tomorrow:

WD Red Pro 6TB NAS Internal Hard Drive - 7200 RPM Class, SATA 6 Gb/s, 256 MB Cache, 3.5" - WD6003FFBX

Will these drives successfully mix, or is waiting for a perfectly matched drive a better solution in the long run? Also, does the Red Pro offer a longer service life…this is my third drive of the four to fail.

from my understanding you have to match rpm/rpm otherwise this could corrupt your backup