Thanks for the reply, Itamar. Yes, I have the latest version of Dataform.
The textarea setting must have set itself to "Moodle auto-format" during the upgrade somehow. Afterwards, I had the dropdown to select the editor type under *every* textarea field in *every entry* of the dataform, however trying to change it in the actual entry didn't work.
So I followed your suggestion and went in the configuration settings and I discovered that it was set to "Moodle auto-format" (which must have happened during the upgrade because previously it was set to HTML). Setting it back to HTML format fixed it and also got rid of the editor type dropdown list after the textarea fields in the individual entries.
Thanks again for the help!