If this is a bacterial infection is unlikely it directly contagious so I wouldn't worry about isolating them.
I suggest ordering the antibiotic as soon as you can. Whatever this is isn't likely to kill either hen in the time it takes before you get the med. Meanwhile, keep reporting their behavior and monitor their poop for any changes.
Also, watch for cecal poop. Cecal poop can be an indicator of a blockage in the reproductive tract. As long as you see regular cecals from both hens, there's less of a chance this is due to egg binding.
I suggest ordering the antibiotic as soon as you can. Whatever this is isn't likely to kill either hen in the time it takes before you get the med. Meanwhile, keep reporting their behavior and monitor their poop for any changes.
Also, watch for cecal poop. Cecal poop can be an indicator of a blockage in the reproductive tract. As long as you see regular cecals from both hens, there's less of a chance this is due to egg binding.