I heard back from WD on Friday. They asked me to download the software mentioned on this URL http://wdc.custhelp.com/app/answers/detail/a_id/940/ and to run quick tests on all the drives. It will require you to be able to connect them one at a time to a PC though, either by a USB dock/enclosure or directly to a PC running Windows.
Then if they are all healthy (mine were) they advices to write zeros to ONE of the drives (which took all night), reconnect them all and see what happens. From reading the different threads from people I think this works for some, unfortuantely for me it didn’t
Important. Number the drives before you take them out as I believe they need to be put back in the same order for the RAID array to remain intact.