Hi Liz,
I would leave things alone. Since it just hatched today, it will still be absorbing the yolk sac, so it might not even be ready to eat yet. If you take the other two out, the parents might abandon the chick. When you stir things up with a breeding pair, you always risk them deciding the nest isn’t safe anymore and they leave it. Hopefully the little one is still getting the yolk sac nutrients, and once it is absorbed, it will beg and get fed. If you hear it peeping, and feel they aren’t responding, take out just the oldest chick for a short time and see what the parents do. The older ones can bully the littlest ones. But again, be careful with interfering. They have the best chance with the parents for at least the first two weeks. Then if there is too much of a size difference, you might need to pull the oldest one to hand feed, if you know how. Cockatiels can be tricky to hand feed, even if some breeders tell you it’s easy. All it takes is formula at the wrong temperature or consistency and things can go wrong very quickly.
Thank you for asking Lafeber,
Brenda