I am not sure what is going wrong. This is my second time hatching coturnix quails. I don't know what information would be relevant so I will just provide all the info I can and hopefully someone can tell me what is happening. Incubated 48 eggs from my own birds. I hatched the parent birds also and they all seem healthy but I am unsure how closely related they are. 1 silver male, 1 gold male, 2 brown males, all females are brown. I fumigated the incubator 2 months ago but did not think to clean it again right before putting in a new batch of eggs 19 days ago. Not sure if necessary. Incubation temperature: 37.8 Celcius Incubation humidity (first 14 days): 40-50 Incubation humidity (15 days onwards): 50-62 13 hatched on day 17. 12 looked healthy, 1 I thought looked a bit weak so left in incubator. A brown one. Around 12-24 hours after this first lot hatched I transferred to brooder and they were eating and drinking fine and running around and not piling on top of each other and not trying to get away from the heat either. Got silvers and all the rest brown. Day 18 some more hatched. The 13th bird was still in the incubator and looked really weak with eyes closed but legs seemed to be seizuring. Left it in there. Took out the other birds. All brown. Day 19 (today) almost every single egg leftover hatched. Some are still in the process of hatching. No deformities. Cheeping really loudly. But within a matter of hours (when I returned to check on them again) they were just laying there with eyes closed and weak chirping. I checked again and saw that almost every single one was dead. If it matters, they were all golden and browns. In the brooder, each morning I have found 1 bird dead, all dying in the same spot under the heat lamp. The other birds just seem to be normal. My silver birds especially seem to be thriving and more energetic than the rest if that means anything. Could something be affecting some birds but not all? Is there something contagious from the later hatching birds suddenly infecting my first birds? Could it be genetic? Bacteria in incubator? Something I am doing wrong? I am not sure what to do. Does anyone know what is wrong and how to stop these birds from dying? I have birds that are hatching right at this moment and I'm afraid they will all die as well.