Hi elweaselgrande,
the limp is a concern, but first things first: I would fetch some coccidiosis medicine and give it to all the chicks in case this is the problem. It's the most common chick ailment and can easily kill, whereas it won't do any long term harm to treat her (following directions...
Hi elweaselgrande,
a few extra details might help people pinpoint the problem. For instance I'm wondering how old the sick bird is (in weeks), what her diet is, and whether she's the right weight (pick her up and feel her breastbone, then compare her to other birds)? Check her nostrils for any...