I have six 4 week old chicks. 2 of which are sometimes mouth breathing and sometimes sneezing. I have them separated from the other 4 now. Since week 3 I have been letting them out of their brooder and roam in an enclosed yard during the day. Back in the brooder at night. 1 of them is more noticeably mouth breathing and was sneezing a fair amount last night. Less sneezing today but still breathing with beak a little open. The other one is not so markedly mouth breathing but I did notice it. They are still happily eating and drinking. And yesterday before I noticed there was an issue- I noted that ALL 6 of them were extremely active and vigorous. Running around doing their usual chest bumps and chicken bombs. But I did not realize that yesterday morning my husband noted that the one cockerel was having an issue. So whatever it is- it was happening before we took them outside yesterday. But I did NOT note anything amiss Friday at all. I am obsessive about this stuff. They are in a cage style brooder, no brooder lights on now, ambient temp at night is 76-78 (they are in our home), and outside during the day (90s) with access to shade, fresh water and food. Substrate up until week 3 they were on pine shavings- cleaned daily. For the past week since they are going outside during the day- just puppy pads changed daily (so fresh pads when they come in at night). I started adding Rooster Booster (electrolytes and vitamin mix) to their water last night. Their poops appear to be normal. Eyes are clear and no snot or runny noses. The one cockerel that appears to be worse I can hear some raspy-ness in his breathing- almost like a crackle. The other one's breathing as of an hour ago sounded clear. They still seem to be as lively as they normally are but the one that is less 'sick' is extremely bothered that the other 4 chicks are gone. He is calmer now. I feel bad for them stuck in a cage just the two of them. Oh and I have NOT been to any farms, no who has chickens has been to my house in weeks and they had no contact with my chickens, I have not been to anyone's home that has fowl...ever. I have been to Tractor Supply of course. Have not been to fairs or shows. But we are pretty secluded out here. I added new chicks 2 weeks ago (in their own brooder and these chicks came from the same breeder, a reputable one too) and 2 goslings (also an entirely separate brooder) from Metzers. Everyone else appears to be fine. If I am leaving anything out please let me know. I have chicken books for days, I have read them and re-read them. I am at a loss. Thank you in advance. UPDATE: I saw one of them shake their head and 'wet' fly out away from their face. Oh my gosh this is horrible isn't ? UPDATE 2: Adding more symptoms. A lot of 'resting', closing of eyes like they are tired. A yawn like mouth motion and sometimes a break shake of their head.