Im so sorry to whats happening i totaly know what your going through. I tried to watch your video but was compatable with the ipad. My 2 month old chick was doing the same, sneezing, head shaking & coughing. I got told to take her to the vets which i did and they gave her baytril for 5 days but didnt work so they tried her on (Doxycyline 260mg) antibiotic. Its an old fashioned antibiotic used to treat respatary deseases in pigeons & pheasants and because i live on a farm she was wondering if my flock was catching this as i had 20 chickens and 15 showing the same symptoms.. To start with i had to syringe the first dose down every chickens throat then put the powder in the water for 5 days making sure they only have access to that water. All apart from 1 chicken are totally fine... And the one chicken who is poorly has a swollen eye so im hoping its not related... I hope you find out whats wrong and your vet can sort you out. Just thought i would tell you my story and hope you dont mind.xxx