Very sick/ weak chicken. Spotted red mites, need fastest cure ASAP!

[Sofi]

One of my chickens woke up today very droopy and weak. She seemed fine yesterday. She won't come out of the coop. Watery stools, closed eyes, dirty around vent. I cleaned her up with a wet soapy rag and saw red mites!! How can I help her?? I am very concerned. I dusted her with Sevin, is there anything quicker/more effective? Can I use cat frontline?

Thanks!!