Just a note on the nestbox cam - size is very very difficult to gauge here because of the fish-eye lens. The lens gives us the whole box but it make the box appear much larger than it actually is - also means that sizes are misleading too - a small chick might not be as small or may be smaller depending on their position in the box. Given that all chicks hatched within 24-30 hours, there will be no size difference because the first three chicks and the last chick. The only difference might be if one egg were smaller (like Mistral in 2007) but all the eggs were the same size when I checked them over not long after they were laid.
And yes, all the chicks look fine. The little chick that "didn't get enough" at the last meal, probably got more at the previous meal and wasn't begging as hard as his/her sibs. Also remember that while they are under Princess/Ivy, we can't see how they are shifting/being shifted, so the chick closest to the camera now will not be the same chick at the next meal.