Since you were able to get a handle on the crop issue, obviously something else is going on to cause the crop problem. SO many things could be going on internally, it is hard to know. Have you felt her abdomen on the outside, from between her legs up to the vent? Does it feel like a water balloon? (compare hers with others). If so, she could have Acsites from internal laying or even a heart condition will cause fluid to leak into the belly.
She could have reproductive cancer and tumors growing in the cavities, putting pressure on the intestinal tract, causing the crop to become slow. Even an internal fungal infection will cause the crop to slow, sour or impact. Sometimes if you do an internal exam through the vent with your finger, you can feel tumors growing.
The only other thing I can think of is Coccidiosis. Not likely, but this can cause diarrhea and have them off food and water. You might try some Corid in her water for 5 to 7 days. It won't hurt her if she doesn't have Cocci. All Corid is is a thiamine blocker, which will stop the cocci from reproducing.