rdm disk mapped to vm but cannot vmotion to another host

I got 2 RDM disk mapped to a vm. ITs 6TB and 3 TB lun. Its currently on hostA

When I try to vmotion it to hostB or C it gives me an error

any idea? When I go to the other 2 hosts and go to Add storage, I see these 2 luns available to add. why is that?