I have had 2 white hens since birth (I am a new chicken owner) they are now 12 weeks old. 2 weeks ago we went to a persons house that sold chickens and bought 12 more, =2 polish, 2 rhode island, 2barred rock, 3 legbar (i think), 2 ameraucana, and 1 welsummer all hens all under 20 weeks old. Within the week I noticed my one white leghorn gurgling a little. I read on the internet that they can make a purring sound, so i let it go a few days, she still made the sound so I went to the feed store and they gave me Duramycin 10, add 1 tablespoon to gallon of water daily (fresh batch everyday). The next week we went to another farm (more respectable-the lady works at a feed store-had a real farm) and bought 1 welsummer rooster about 11 months old, 3 silkies bantams born in may, a qual belgian bearded danver hen-bantam -not sure how old she is, but young. Since last weekend, now both white leghorns., my little quail, my large barred rock, 1 Ameraucana are sick, sneezing or coughing, runny nose, gurgling sounds in throat, shaking head like to clear themselves, seem sleepy during the day, diahrea and their breath will knock you out. Also 1 of my barred rocks my little one had-had a runny eye, it is gone but the area under that eye is swollen. They are still on Duramycin 10, and also have them on a electrolyte that Tractor Supply gave me for them at 2 1/4 teaspoon added to the same gallon of water. Today, I called my lady back at the feed story, she said bring 1 leghorn in and she would sell me tylan 50 to inject in all my sick hens. She showed me how, she injected it in her left shoulder area at 1/2 cc and told me to inject the other sick hens alsobut only once. She told me to give the qual and bantam 1/4cc. I read to inject them for several days???What do you think? Am I doing the right thing? Are there shots I can give them all later so that this wont happen again if it is Mycoplasma or CRD, corzya, or whatever. AND if they live will they always be carriers and with that I cannot ever buy anymore chickensor eat their eggs??? UPDATE-TODAY now my black silkie sounds terrible, gurgline while breathing in and out, and sneezing like every 15 breaths, sleepy. I couldnt smell her breath -couldnt catch her, she is fast! My other sick birds still sound and act the same.... I am really upset with myself for not being more careful I guess with the first batch I purchased. BTW, my pen and coop are brand new, very clean, concidering they are messy, I wash their water thing, etc... Please If anyone can give me some advice, they are also our pets, and well I love them..... UPDATE-Now my new little qual chicken who doesnt feel good, even though she isnt as bad off as the others that are sick, literaly is coming up to me to hold her, she nessles into my lap and seems to be sleeping, she has always been friendly but never this loving, she seems to be last in the pecking order, but now she just wants to be held. Trying to find a chicken vet, not finding anything yet, put in a few calls, waiting.... my poor babies, I am so worried.