Great Tit parent not returned

We have a nest box of Great Tit chicks ready to fledge any day now. However this morning one chick died and was too large for the parent to remove from the box. We waited for the parent to leave and then removed the deceased chick. We watched the parent come back a handful of times after the removal to feed the remaining chicks but have not seen any parent in over 12 hours.

Is it common practice for parents to not return to the nest to encourage chicks to fledge or should we be worried that something has happened to the parent/s?