Oh wow! Didn't realize you were a native Kansan. I love Yoder, we go down every now and then and buy up baked goods and pies. You have a respiratory illness or diesase going on. The popping you hear is common and is related. It's most likely fluid in the lungs-- BAD. I would say to treat with VetRX, but since you already lost a bird, this sounds much more serious. And the popping noise would indicate a much more aggressive illness. I would get to your vet and ask for injectible Baytril to give them. No more than .5cc a bird. It's not that expensive-- I paid about $30 for half a vial and ended up injecting several birds when I had something go round. Don't over dose them, the Baytril is ONCE a day. My vet had told me twice a day, and I came home and did my own reading up on it because that sounded like an awful lot of drug. Indeed, it would have killed them, and I'm glad I had the sense to double check him. My vet refuses to do blood work ups on birds, he says they are carriers of EVERYthing and to pin point down what exactly it is that is causing the trouble could be difficult. So we run a broad spectrum antibiotic and hope for the best. Necropsy can be done after the bird has died to see what killed them. Not only that, but it is very difficult to get enough blood to run a lab while they are alive. Unless you have an entire flock sick and don't mind sacrificing one to save the rest for the necropsy.