HP Proliant ML350 G6 Raid Issues

[LeeVest]

Hi my customer has a HP Proliant ML350G6 Server which seems to be having RAID Issues, it is setup with P410i controller (Firmware V3.0) and 5 x 250GB hot swap SATA Drives on a RAID5 cofiguration.

A week ago there were complaints of performance issues with the server, while diagnosing i checked the ACU which showed everything was fine, i then ran HP insight diagnostics on the drives which came back showing drives 2,3 and 4 were failing with high amounts of read/write errors and to replace.

I ordered replacement drives and attempted a hot swap of drive 2 yesterday, it started to rebuild the array and took about 12 hours to get to 100%, it then came back as drive failed and put the array into Interim Recovery Mode.  I am after advice what to do next, do i try another new drive in the same bay or could this be controller/bay issues?

Thanks in advance.