Can you format one of them? Or do they all contain important data?
Any way, did you see those IOStorageFamily i/o errors at boot screen on your machine?
log show --predicate 'process == "kernel"' --debug --info --last "1h" |grep disk2
2017-10-09 00:10:24.555774-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:24.731039-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:24.910084-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:25.091361-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:25.260548-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:57.794501-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:57.965587-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:58.139814-0400 0x526 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:58.322978-0400 0x1970 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.
2017-10-09 00:10:58.512175-0400 0x1973 Default 0x0 0 0 kernel: (IOStorageFamily) disk2: I/O error.