The same thing happened to one of the faverolle chicks I hatched last fall. I gave him a few drops of baby vitamins 2-3 times a day and two days later he was fine. Turned out to be a vitamin deficiency. This may not be the case for your chickie but it's worth a try.
Yes, liquid - I used poly-vi-sol NO IRON. The first couple days I'd put a drop or two on his beak and he would swallow it after he started doing better I put 1/2 dropperful in the water daily. How old is the chick? Mine was about 2 weeks old when he started it. Try it - if it's a vitamin deficiency, it will clear up quick. Good luck