HELP!!!!! My chicken is behaving very wierd????????????????/

Hello, this is a response to my preivious post about an hour ago (below). with help from you guys, i have transported my "tail droopy" chicken inside our houseer tummy- it has nothing but water in it. i made a mixture of yogurt and shredded apples (very helpful in the past) and i fed about a teaspoon to her but i'm having trouble opening her beak any more she at a very tiny amount by herself. She is standing in place, a little low, and moves around barely in her mini cage. also, the feathers near the end of her tail/on her back are very fluffed up, gives a visual apperance that there is a bump there (but there isnt) please help!
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Yesterday, i had a little emergency so i forgot to feed the chickens before i got to bed so they were hungry all day. today i came back and fed them immediately, i gave them 1/3 scraps, 1/3 oats which is really good for their health, and a very small handfull of this bird food mixture (me and my mom: were trying this new stuff it doesnt say whether or not its for chickens but it has corn kernels, sunflower seeds, and such). well, i gave them the food and let them open to run around, at first they pecked at the food. i came back an hour later and the food was untouched! i noticed that they had pooped in the water so i changed the water and the 2 of the hens at them and one of them didnt- she was the one of the the hens standing in the corner with her tail down and eyes open and walking a little lazily. i closed my chickens up so they could go to sleep and that hen went to the corner and sat down. now im inside. i reallly love my chickens, i dont know what is happening! a few months ago i bought this stuff that helped the chickens if they had watery poop but i never used it. should i use it now even tho they don't have watery poop? by the way my chickens are of old age about 3 years old. please help!

PS thanks for everybody who have helped me out in the past