One of Claire's chicks seems to be rather more advanced in its development than the other. This chick is often seen out of the nest cup as is shown here.
The great tit chicks will be gone soon. Tomorrow it will be 20 days since they started hatching - the average period of time before chicks fledge. Having said that, they have so far shown little sign of wing flapping, a necessary precursor to fledging so perhaps we will have them a little longer.