Tips for raising a runt?

[Antomongis]

Does anyone have advice on caring for a runt. I have two chicks, 5 days old, one a male and one a female runt. They were given to me to foster for a farm so that the runt could have a better chance. I have never had chicks before. Any help would be appreciated! I attached some pictures of my chicks.

 

[JacinLarkwell]

Curious on why they're so sure they're runts that young. Mine blended in until the others started feathering out

 

[Antomongis]

Curious on why they're so sure they're runts that young. Mine blended in until the others started feathering out

This one is super clearly a runt. I once fostered a runt quail that was the same way. Sadly, he did not make it. He passed after a month and I do not want this to happen again. She has difficulty walking, trouble flying short distances like the rooster can, and sleeps much more than him. Her wings also resemble a moths wings, they are super thin and she doesn’t have much control over them. She gets stepped on all the time by the other chick and he weighs like twice as much as her. She just looks underdeveloped, similar to a premie infant.