If you look closely, you'll start to see proper owl feathers developing on the chicks. Small Spotted Eagle Owl feathers replace the white fluff.
The other thing you'll see is one of the chicks has a much darker face than the other two. There is one very tiny one (in comparison to its siblings - quite normal for this stage of their development), which only leaves one other chick. Each chick will begin to develop their own personalities. One might be curious and want to venture far to explore. One may be shy. From the appearances and personalities, we'll be running a "Name the Chicks" competition through Africam.com