At 3 weeks old they need at least 75⁰F measured at the bedding level. They are not acclimated to lower temperatures because they could get under the mother anytime they felt the need. They are definitely not acclimated to your nighttime temps.
Until you know they are eating you may want to...
If the new ones aren't used to being around people they may be terrified. It also matters what temperature they were acclimated to.
If you have them on wood shavings, make sure they have appropriate sized grit available.
Try to observe them from a distance if possible to see how they act when...