How do I understand and manage subscription?

I have a VNXe3200 that I would like to update to a newer firmware. However, on running a health check I get an error:

One or more storage pools may not be in a healthy state. Upgrade may continue, but the recommended course of action is to record this output and contact your service provider. [Error Code: flr::check_if_storage_pool_recovery_is_required_3]

The provided link gives me no results, however searching tells me that this may be an oversubscription issue. The storage pools all show as "OK" in the Storage Resource Health tab. In Storage -> Storage Configuration -> Storage Pools, however, three pools have gray "i" logos and are over the capacity thresholds.

If I have the space, do I just need to migrate my virtual machines to new LUNs, delete the old ones, and migrate them back? We are not actually using anywhere near the percentage that the system claims.

Interestingly, one of our pools that has a green check mark is at 145% subscription. I don't understand how this is possible. The subscription is for 1.0TB but the total pool size is 728GB, with 272GB available.

So, a second question, how do I find out why a pool is oversubscribed and how do I reduce that subscription?

I think I have enough space available to shuffle things around if I have to delete a LUN, and I can plan on that during our next maintenance window, but I really need to make sure I understand the problem before I start doing that.