Edit: im not sure ypu have mites. Bugs always are attracted to open eggs. Here i get ants. Mites usually infest at a later age. Still do a checkup on the mother as they can transfer from her. But you can probably put them back with her in a new nest. Also careful with the heat lamp, make sure they also have a place outside of the heat. The best heat source is with the mother.
I have mite infested areas and have lost entire bantam broods to mites, but it happens over the course of a week or longer. Now i keep small broods of only four and keep close watch on the infestations.
Black ones are not settled yet, and they turn red when they are attached and eating the blood. Then it's really hard to get them off. Look for red clusters on the face, around the eyes, around the beak, around the ear holes. The red spots are where the mites have dug in to the skin and are eating their blood causing pain, lethargy, and death. But usually it will take a few days of lethargy, mites wouldn't kill four overnight.
So I would like to help figure out what happened, and if possible get the babies back to the mother if possible. Do you see the mites on any of the babies now? What about the mother?
Provide the mother a dust bathe. I don't know your setup or how much space you have. But if the mother has access to a place to dust bathe, she will take care of herself. She will also teach the babies on day one if she can.
Examine the mother for her health. Examine the babies for red clusters. Examine also for individual mites. Use a magnifying glass and good light if available.
My current best practice for cleaning the mites off the babies is an internal medicine such as ivermectin that says 'internal and external parasites'. Edit: But this is for babies that are older than a few weeks. You can try to scrape at the red clusters with a toothpick and alcohol, but i have best results dabbing a natural oil on them, i assume the oil suffocates the bugs. I use aguage oil, but coconut oil may work. They are really hard to get off and i have only been able to save the ones that get both medicine and an external cleaning. I have had best luck covering the mites with oil and scraping the skin with a toothpick until the mites are no longer sucking the blood, but it is a fairly difficult procedure, unless you have a magnifying glass and good light.
