huh, I know cocci is common, but why, besides her age, are you thinking cocci? she has had no droppings and a full crop which has not gone down overnight. doesn't that point to impacted crop vs cocci? I appreciate your thoughts!Do you have corid? The first thing to do is treat for coccidiosis.
Edited to add: I just read the first post--natural chemical free--
The chick likely has cocci. You can try plain yogurt and whatever vitamins you can give and be chemical free. Cocci can kill in three days depending on how bad the load of cysts are.
Going the natural way, to build resistance in the flock, you may want to cull her, meaning to not use for breeding.
Look up coccidiosis. It is very painful for the chick. euthanize if she is suffering too much.