Sick chick- won't eat or drink on her own

My little one is about 6 weeks old. Her brooder mates are all healthy. Hatchmates are running about 260 grams while she is at 117 grams. She is very weak, but no other real symptoms. When I first found her, she couldn't hold her head up, and rested back on her rump unable to stand on her feet. She was immediately removed and placed in isolation on a low heating pad. I am force feeding her around the clock by gently opening her bill and putting a drop of fluid just on the tip. She will swallow with this method, but will not choose to eat on her own. I am trying different preparations through the day. I made her some scrambled eggs mixed with some finely crushed chick granules and nutri-drench. I've made electrolyte/probiotic/nutridrench water and dropper fed her. She did like thin yogurt and didn't fight me to eat that. What else can I do for her? I do know she has mites so I bathed her in DE, carefully avoiding her face, but ensuring it got down to the skin. How can I get her to gain weight? I think she might be getting a little stronger because she is starting to fighting her bill when there was no resistance a day ago. Picture 1 is her poop today. Picture 2 is her 2 days ago, resting backwards on her rump. Picture 3 is her actually sitting on her feet again. Any help appreciated. I can go to Tractor Supply later today and get anything she needs. Thanks!

Thank you for replying. I'm glad she made it. I'm so hoping I can save this sweet heart!

Please go get some Corid right away from your farm store or tractor supply, and start treatment for coccidiosis. That is the most common problem in a chick that age, and they get it from the soil or older chickens. There looks like there could be some black old blood or some rust colored droppings. Corid dosage is 2 tsp of the liquid or 1 1/2 tsp of the powder per gallon of water for 5-7 days. Treat all birds, and change water each day. After you finish treating, give them some vitamins, and probiotics or a little buttermilk for 3 days.

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I have Corid on hand, so I'll start that right away. Do you know if it loses effectiveness if it has been open awhile, like 6 months, but in a ziploc bag?