i don't think limestone grit is the right kind of grit. i believe it is soluble... you need insoluble grit for them to be able to properly digest their food. (granite grit)
I agree on the grit, it needs to be like regular gravel. Also, if you pull pieces of grass that are too long, they can get impacted crop from that. I learned that the hard way with my Speck. Sussex pullet.
It has a face like a crow. Really interesting. It gives new meaning to the term "strange bird".
Don't you love this site! You ask a question and get the answer to another. The person who told you the chicken has "sour crop" and how to treat it, may have saved your bird's life!
I hope she gets cured. We need more "strange birds" like her.
I'm so sad that you lost your chick. But thank you for sharing your story with us. I learned a lot about impacted and sour crop. I'll be on the watch for it.