Ordinary chick starter, made wet with water.
Some chickens like it runny and soupy, other chickens like it stiff enough that holds its shape as they take bites.
Sometimes just changing the texture of the feed (like adding water) can help a chicken eat it better.
And chick starter really does have all the right nutrients for growing chickens. It sounds to me like she doesn't need special food, she just needs to eat enough food.
You could try giving her a private meal in both the morning and evening, in case the other chickens have been interfering when she tries to eat. (Sometimes not eating is a physical problem, sometimes it's a social problem.)
I was not able to see either of the two videos, so I'm saying this based on what was in the text.