Most of my birds are on sand, but I still provide grit for them. Do you have her quarantined? You should separate her from all other birds, in case she has something that they could get.
You could try gently massaging her crop. You might want to research sour crop. But, I am pretty sure...
Corid is for Cocci, does she have any blood in her stools? If not, then I wouldn't recommend giving her Corid. She may have gotten chilled. Have you wormed her? Does she have a runny nose or any type of discharge from her nose or eyes? Do you see any tiny bubbles in her eyes?
Is there...