Need urgent help! Treating for bacterial infection but now suspect Sour Crop (liquid draining from mouth, not eating)

Hey everyone, I really need some advice on my hen. She originally had a messy vent, so I started treating her for a bacterial infection with Doxy/Tylan. She is currently on day 1 of a planned 5-day course. She drank a tiny bit this morning but isn’t eating.

When I got home from work, I noticed she had liquid dribbled all down her front (attaching a picture). Someone briefly mentioned "sour crop" to me but didn't give details.

If this is sour crop, should I stop the antibiotics since they might be feeding the yeast? Do I withhold food and water tonight to let her crop empty, or will that dehydrate her too much while she's already weak?