Oh, sorry. You said water poop. She may not be eating enough. Can you wet some chick started with warm water and see if she’ll eat it? You can also try scrambled egg for a protein boost. Has she had access to anything besides chick starter? If so, she needs grit to digest it. Please keep us posted.
Poor baby looks ill. Injury is possible, too. Please gently look her all over for injury. See if she flinches when being touched anywhere. I would separate her into a warm, quiet place so you can monitor her. Can you add poultry vitamins to her water? Is it possible she was bullied from feed...