Info/Background: My girls where born this year in March. I have RIR, Black sexlinks and Bard rocks. I have 12 total! On Wednesday this week I noticed one of my girls (a Black Sexlink) started weezing and coughing. I went to the feed store and they told me to give the flock poltry cell and Duramycin - 10 (tetracycline). The antibiotic is mixed into their water once a day for 6 days. This was started on Wed. The chicken that was originally sick was doing great the next day however, Friday morning I noticed a different hen (a bard rock) acting very tired and not interested in doing anything. By Friday afternoon there where 2 Bards acting like this Everyone else is free ranging and they are just sleeping. 2 other chickens (A different bard and a different Black) are free ranging but one eye is closed. The whole flock sounds/looks snotty, but 8 are still acting normal. I did separate 4 the bad ones. On Sat morning all 4 that were starting to look bad looked worse, so I went out and got Tylan-50 and began shots ½ cc 2x a day for all 12 girls. First shot was Sat afternoon. The 4 did not eat or drink Sat. On Sunday the 4 still were showing no improvement L I mixed their dry pellet food with water and plain yogart and got all but one to eat some and drink. The same 4 are still looking bad today. We do not have a vet that will see chickens where I live, but I was able to bring a fecal sample to my dogs vet and there are no worms or coccidia. Crops are empty. How long can they go on like this?