Do the LUNs currently show up as snapshot LUNs if you run:
esxcli storage vmfs snapshot list
Without knowing what was causing the LUNs as being detected as snapshot LUNs, it's hard to say what needs to be done. I'd actually double check how the LUNs are presented to the hosts (on the storage system) and - if there's nothing unusual - persistently mount the LUN next time. Since the non-persistent mount (lower-case "-m") worked for you, I would not expect any issues with the persistent mount.
André