I am praying for you also. I didn't know this about yougart. My favorite cockerel (young rooster, Little Baby), got very sick very quickly, all at once, and his symptoms were the same as your Fluffy. He was sneezing, coughing, mucas and swelling in nostrils and and eye, one eye stuck together, mucas in his mouth, ratteld breathing, yellow diarreha, feaver, wouldn't eat or drink, just standing still with eyes closed. I built a big cage for him and took him inside and put a heat lamp on him (cage is big enough so he can back away from heat, and light is not too close, cause the heat light can get hot). On advise, I went to feed store and got Tetracycline, and began to mix 2tsp per gallon of that with water, along with 4 TBS Apple Cider Vinegar and about 1 tsp electrolytes. Since he wouldn't drink on his own, I got a cough surup measuring cup and poured some of that water in it, along with a little extra tiny pinch of the Tetracycline, and drew it up in a syringe (without the needle), and I started giving that to him 2 times a day. I also got some yougart and did the same with that. And I had to keep his nose cleaned out (very carefully with toothpick and Q-tip) They can't breathe if the nose is stopped up. He gradually started drinking water on his own, and then eating a little bit. I fixed him some scrambled eggs, and some rice. The Apple Cider Vinegar in the water, cuts down the mucus, I could tell the difference after I started using this. The main thing was first to keep him very warm. They told me about 85 to 90 degrees. And keep her out of drafts. I went a couple of days ago and got some VetRx for them also. It's like Vicks Salve for chickens. I warmed it and rubbed a little on their heads and under their wings, so when they sleep with their heads under their wings, they can smell the vapors. I also put it in my vaporizer and have it in there with them once in the day and about an hour or two at night. But mainly isolate, warm, hydrate, first thing. They Tetracycline has helped also, but I have ordered some Tylan 50 injectable from Revival Animal Health.com, but then I saw it at 
Tractor Supply Company, when I got the VetRx. The person who told me about it, said they gave it orally 3 nights and it cleared up hers that had these same symptoms. So when I do get it, I plan to give it orally, in the syringe without the needle, I just can't give shots, so I'm glad it can be done this way. Depending on the weight, size of the chicken would be doseage. She either said 1cc or 2cc. (I don't remember), but someone on here would know for sure. I have it written down in my notebook somewhere. But anyway supposedly this drug works miracles and quickly. I don't have access to a vet that treats chickens, so I just have to try to do it myself.