I have nothing collected. I have been relying on Proactive DBA and it was shut down during the period.

I can only see metrics in august and now.

I think that this is related to spilling to tempdb. In august tempdb IO is around 10-30 ms and at the worse time it was around 3 s.

At the moment IO is around 1.5 s.

I added one missing index and changed one view to use UNION ALL instead of UNION.