Wonderful suggestion on the Apple Cider Vinegar! Probiotics work well too for chicks. Both help get the GI tract in good order.You're lucky you can get it. I have to go through a vet.
Another thing that can be done (and this has been PROVEN to work) is add a drop of active apple cider vinegar to their water. There are dosages online, bit it's very minimal.
I know everyone claims that ACV is a cure-all and this and that, but actual research has been done on this by actual universities.

