Great Tits - mother went missing

Been monitoring a nest box via camera for the last few months.

The second breed of Great Tits was going well until a couple of days ago. Sadly it seems that the mother went missing. Didn't spend the last couple of nights in the nest and feedings became infrequent. Two out of the five young ones are still alive and the father feeds them periodically.

Is there anything I can do to help??

- Andreas