Some MySQL databases no longer visible under "Edit databases" in Virtualmin

The "Edit databases" screen for some, but not all, of my users have lost their MySQL databases. All that is displayed is the default postgresql database, and no MySQL dbs, even though I am positive that these DBs exist--the users' websites which use databases are still operational. How should I go about investigating this?

I have not changed any configuration beyond increasing the number of file descriptors available to MySQL as that had started causing some lock-ups. Thanks.