Display image sizing

In RT (Directory Theme) I have my thumbnails set to 199 x 300 in WP media settings and it works for all listings made in RT, however those made before in 7.1.4 (and earlier) are not re-sizing and therefore creating a lot of white background space.

I believe that this is because those older listings pull from the old display image field.

Is there a way to update the old display images?

Any help appreciated.