You can manually merge those albums back together, but the worst-case scenario might be to Plex Dance the songs. If you have the metadata in your files accurate, Plex ought to accept every song in the folder as part of the same album.
I use my own metadata, which is kinda funny because my metadata is pretty hosed. I’ve been slowly working on adding the metadata back in (Thank you, MP3Tag and MusicBrainz!), and keep finding albums that are all broken up like what you got.
BTW, after you change some file metadata, try telling the library to scan. Even simple file renames seem to cause Plex to think that they are new files, so the dance sometimes isn’t necessary.
