Yes, and there is:
Mar 19 20:20:49 IWURSRV kernel: mpt2sas_cm0: mpt3sas_transport_port_remove: removed: sas_addr(0x4433221101000000)
Mar 19 20:20:49 IWURSRV kernel: mpt2sas_cm0: removing handle(0x0009), sas_addr(0x4433221101000000)
Mar 19 20:20:49 IWURSRV kernel: mpt2sas_cm0: enclosure logical id(0x500605b003cc0de0), slot(2)
It is a strange issue, since it keeps happening only with those two disks, if it's not power/cable could be a controller or disk problem, can you connect them, even if temporarily, to the onboard SATA ports?