Urgent advice needed for blue tit brood

I have a camera nest box in the garden with 11 six day old blue tits in. Everything was fine until yesterday morning when the mother has gone missing. I guess she's taken by a predator. Father has been in and out all day and this morning feeding and removing waste, but I'm worried that he's got too much to do. The chicks stayed on their own overnight and I'm worried that they'll get cold or abandoned and all not survive.

Can anyone suggest anything to save the brood? The garden has feeders of heart seeds and fat balls.