Assuming the iSCSI storage systems uses the ESXi host's iSCSI IQNs rather than IP addresses to recognize them, and you are using Software iSCSI on the ESXi hosts, then w- with re-installing the ESXi hosts - you'll end up with a new IQN for the host which you need to introduce the host to the storage system. On the storage system you certainly want to delete the old host object.
André