Current alert - all my drives are causing slow I/O my pool Main(RaidZ2)

Hi,

I have just upgraded to TrueNas Core from FreeNAS 11.3 and since then I am getting those alerts.
So far all the drives are reported to be causing slow I/O on my pool Main.
To be noted: I have both a log and cache on this pool

I have 2 kind of drives:
- WDC WD20PURZ-85G (WD Purple)
- TOSHIBA MG03SCA200

I have 4 of each in a RaidZ2 pool.
I understand the WD Purple are not great for the job but that's all I have at the time.
However all of these are CMR drives if I am correct?!

Is that...

Current alert - all my drives are causing slow I/O my pool Main(RaidZ2)