monitor them.
actually, you might not see much evidence that they have nursed the first couple of days as the mother's milk does not really come in for two days.
is the shed in the shade?
on hot days. the kits may be too warm in the nest with fur and might move out to be on top of the hay and be more spread out, but will move back into the fur together on cooler nights. this is fine as long as they are not outside the nesting box and on the wire. they self-regulate their body temperatures usually.
do check on the kits and handle them a couple of times a day 