Starlings can be quite shamelessly prolific but I too am concerned that this is a little late in the year. However i have also been reading quite a few reports of animals breeding out of season due to the erratic weather patterns. If you count back to when the eggs were laid, it was still quite surprisingly mild, if not Indian Summer-ish, so it probably just put them off their game. It is quite possible that now food is getting scarcer, mum and dad have turfed the younglings out because they are unable to feed the mob now it is a bit more wintery.