Individual . Especially if they are close to a sell by date . If left together , it takes longer to freeze and longer to thaw . Maybe going forward you'll only want to do one rack as part of another cook .Any problems freezing them in the packaging they come in or is it better to individually vacuum seal each rack?
Wash them down and pat them dry before you vacuum seal while using the 'moist' option to ensure a good seal. Your biggest concern would be bones poking through the bag.I would freeze them individually as would be easier to store them in my already full freezer but I'm looking at all that liquid and thinking even when I drain it still going to be a mess using the vacuum sealer on ththem.
That or just partially freeze before sealing.Wash them down and pat them dry before you vacuum seal while using the 'moist' option to ensure a good seal. Your biggest concern would be bones poking through the bag.