Editing the tags after the items has been already added to Plex will sometimes not change anything. Cue the Plex Dance (you can leave out step 4 with music content)
Plex only supports one AlbumArtist per release. So these releases are either all getting combined under Christina Aguilera, or (worse) all albums by Christina Aguilera will be shown as “Christina Aguilera featuring [soandso]”.
Decide on the main single artist for a given release. Then move the album to the appropriate artist folder and embed only this one name as AlbumArtist metatag.