When you refer to your hatchlings as being black, do you mean that they are truly black (or extremely dark brown), or that they have no lighter spots, or both?
One of my females is predominantly black, and has produced hatchlings that have not had any lighter spots on them. They don't appear to be having any problems, but it can be challenging to judge with hatchlings because they can easily get to a point where they're beyond help without showing dramatic outward signs of distress.
The ones you'd acquired may have had some other congenital defects or problems, and the fact that they also happened to all have been black may be coincidental. Or, maybe being completely black is a sign of ill health. In other words, they may have been doomed before you got them.
Learning as much as you can before starting again is definitely a smart thing to do: glad to hear you found a school to do the necropsy.
Right now I'm puzzling over why only one of six hatchlings is showing signs of MBD when its five clutchmates are fine: they are all housed in the same place, eat the same food, are exposed to the same temperatures, humidity and light. The light bulb's UVB element had fizzled and I've since replaced the bulb, and the little guy in question is already improving. But why only one hatchling and not all?
There is so much we don't know.
Regards
Stephanie