Are those photos from today?
Looks like a wrapped up membrane and perhaps some lash material was expelled.
I would not give the whole flock Enrofloxacin, only the sick bird. If you wish to just dose her then use the Amoxicillin, but the Enro is a stronger medication.
Amoxicillin dosage is 57mg per pound of weight given orally 2times a day for 7-10days.
I'd still continue to address the crop/digestive issue. See if she will eat her normal feed. Again, crop/digestive issues are often a symptom of an underlying condition. If she's suffering from reproductive problems, then this can cause the system to slow.
Not that unusual for them to be standoffish when being treated. They learn they are going to get handled or medicated and perhaps don't want to be bothered, don't like the meds or whatever. Sometimes you need change tactics and go out early, grab them before they come out in the a.m. to administer medications, then wait until dusk when roosting, grab them again for the second dosing.
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