Ignore that last post please, I'm now convinced they have cocci. I'm looking for treatments online so if anyone knows of any ways to prevent this for future flocks/easy treatments I'll greatly appreciate it. Sorry for being so hasty and jumping to conclusions, I just really want to keep them all alive, you know?
Thank you all for your help.
Update: Basil has calmed down almost completely now, she is sleeping well and is just sneezing a little bit now. I think she'll make it through the night. In the morning I will rush to get some vitamins as some posters suggested and will continue trying to keep all my chicks alive. I think I may end up pulling an all nighter at this point just to keep an eye on her, I refuse to let her pass if there's anything I can do about it!