I think the chick that hatched at 19th May is only 2 days older as the last, smallest chick.
There is nearly no difference between the oldest and the second eldest chick, they nearly look the same.
The difference of age is 2 days.
The smallest chick hatched at 22nd May, is 2 days younger than his second eldest sibling and is much smaller than him and does not seem to develope as well as his siblings do.
Maybe Cico notices that something goes wrong with him.
