Makes so much sense. It's the same with all animals, people included. Hydration is the key to health.The hard crop lump is likely related to her not drinking on her own. It's probably causing constipation, as well. All of these are good reasons to try the salts flush. If you can get a tubing kit from a vet, that would be easiest. They can show you how to use it, and if not, I will instruct you. Syringing the fluids into her crop would take much longer and wear her out.
Those chickens that appear not to be drinking should be given fluids any way you can. Dehydration will cause a chicken to be weak. Weakness affects appetite, and that can cause dehydration and starvation. These make the antibiotic impotent to help your sick chickens.
The bad smell can be related to fluids and solid material backing up and remaining in the digestive system too long. Making sure the chickens are all getting enough fluids is the most important issue you face. Everything else follows.