Every bird is different. You gave strong meds, it takes a while for the body to recover. Make sure you are putting ACV in the water, they have sunshine and exercise and good feed.Update:
We finished the course of antibiotics, and I hand fed the sick birds until they improved. Both girls are actively eating, scratching, running, and drinking. They seem totally better except for 2 things: both hens are sort of chirping? Or coughing? I'm not sure what to call it. It's loud though. I can hear it from inside the house. Also, neither bird has started laying again yet. They don't lay much this time of year anyway, but how long does it usually take sick birds to recover?
I'm still not sure what they have.