First off a quick history of my chickens; I purchased them at 2 weeks old off of a lady who was experienced with chickens - I bought 3 ISAs and 3 Australorps. They are now about 2 months old, feathered and doing well! However about a week ago I noticed all 3 Australorps breathing with their beaks open, making crackly sounds and not eating well. Long story short I took them to a specialist vet who told me about Chronic Respiratory Disease. Being a beginner chicken owner I had no clue what to think! She assured me that I had caught it when it was mild however I still have some questions that I need answering as I'm worried that they'll get sick again and would hate for them to be in discomfort due to my lack of knowledge. After a 5 day treatment of antibiotics in their water (for the ISAs and Australorps) the Australorps started eating well with no symptoms of CRD. I found it odd that the ISAS did not get sick as all my chickens live in the same flock/together. Is there any reasons for that? Also is CRD a lifelong disease or can be cured through medication? Does the medication cure it fully or just lessen the symptoms? Also is this a recurring illness? Could there have been anything I could have done to prevent this? I've had no other contact with other chickens etc. (as I've read that disease can transfer by clothing, touch etc.). Is it safe to eat my chickens eggs if they have CRD? Sorry for all the questions but I'm still so unsure about this condition and am worried that I'm not doing all that I can to prevent it/treat it. Is it okay to keep my ISAs and Australorps together now? As they've been reunited since my Australorps health recovered. Any extra information on watching out for disease, preventing it or general info about what CRD is, how it is obtained and how to treat it would be so helpful! My Audrey chickie as seen in my picture is doing so well and I'd hate for her to get sick again!