Override of existing rel attributes

Hi!

We were hoping to update the rel attributes of all the links we have on our website that were created using the ThirstyLinks plugin.
However, the new links do take the new, manually set attributes (through Link Appearance in the plugin settings), but the ones that already exist do not. For us, that means redoing thousands of links.
Is there a workaround for this, perhaps an update in the works?
Might this be a conflict with the External Links plugin, that overrides the values with its own?