Backing up from one external drive to second external drive

On my iMac (Mavericks) I use time machine to back up both my internal drives to two external drives. This works well. However I have moved all my photographs from one of the internal drives to a third external drive (Formatted MacOS Extended (Journaled)) and wish to include that in the backups. I have removed this drive within System Preferences "Exclude drop down box" but still can't get it to backup. I have also made this new drive a "Shared Folder" through Get Info. Any help would be appreciated.

John