The RAID set lost blocks

We recently swapped out a couple of failed drives from out PS6500. We now have healthy drives but we now see a "RAID set lost blocks" error. It's running RAID 6 and is a 70-0202. The firmware is V8.1.1 (R417753).

I've checked through the volumes but can't find information on these lost blocks.

This is out of support and I'll confess to have only ever worked on HP storage arrays previously. Does anyone know where I should be looking first ? Or is it best just to raise an out-of-warranty support ticket?