Here is a good article about crop problems to read:
https://www.backyardchickens.com/articles/how-to-treat-sour-crop-and-impacted-crop-and-how-to-know-which-one-youre-dealing-with.73607/
Sorry for your loss. I lost 3 of my original remaining flock a couple of years ago to a bobcat in the middle of the day while free ranging.
Do you have granite poultry grit available to the hens to take in a separate container than feed? Do they have water available at all times? In this time...