I have a brooder with 5 chicks in it. They are probably approaching 4 weeks old. One of the chicks is not growing like the others, and I can't figure out what's wrong with her. She stands under the heat lamp with her eyes closed. I thought she was sick or maybe got too cold for her size, so I removed her and placed her in her own smaller quarantine area with her own heat lamp and food, and water with electrolytes & probiotics. I'm new to chicken keeping, and I'm ready to pull my hair out. Within a couple days she was acting brand new, running around her area scratching, dusting herself, eating and drinking normally. At this point I figured she was not sick, but probably got cold or perhaps was getting manhandled out of the food since she's smaller. I put her back in the brooder with the other chicks yesterday and she was reasonably happy, eating and drinking, and last night she was cuddled up with another chick. I check on her today, and we are back to square one with her standing under the heat lamp, eyes closed, droopy wings. I don't want to lose her! I clean their area regularly, new food and water daily, they have two food areas and two waterers, one plain and one with ACV, access to chick grit and their food is medicated. I don't know what else to do. I observe them where they can't see me and they don't bully her. They basically ignore her because she stands to the side under the lamp.