Alice was the poor victim of being fragile and small - sharp talons and food fights are dangerous, injury is always a danger - hence she was very vulnerable and injured this week.
Similarly, Roo was the little one, tired, hungry, unable to shred, weak, and exposed to the cold for a long period - Sydney was away for many hours – there is also discussion about respiratory issues, if you recall the "cute" snoring whistles - Syd senses things better than all of us, hence nature takes its course.