The chick likely has a spinal cord and/or brain genetic defect. It's not going to get better, and trying to treat it only prolongs the acute suffering.
Roll the little thing in a paper towel. Locate its head and with sharp scissors, simply cut it off. This ends the life without any pain or further suffering.
Roll the little thing in a paper towel. Locate its head and with sharp scissors, simply cut it off. This ends the life without any pain or further suffering.
I'm sorry Belle 
It probably had a problem that couldn’t be fixed, and that’s why it was left at the feed store. You were very compassionate in trying to help.