This can easily be done via your Spitfire Audio app.
Open up the Spitfire Audio app and log in with your account email and password.
- Select the library you wish to re-download the update for
- Click on the cog next to the word installed and choose reset
- When prompted, choose reset to latest update.
- This will reset your latest update, if you do not see this then restart the app and it should appear.
You can repeat this process for any other updates you wish.