Jan-
I have to agree, this does not look good. We just had an almost identical situation to this. It was a small clutch (17) of veiled eggs. We too had used the exact same vermiculite since we did not have any coarse grain at the house. They had been kept at low 70's for their entire incubation. About a month before they hatched we moved to a new place. At the new place we kept them in a closet which we thought were the same temps.
What had actually been happening was that during the day while at work temps in the closet were reaching nearly 90

and dropping back down by the time we got home. The only reason I knew this was by peeking in there one weekend while at home mid-day. They had been in this closet a few weeks before i noticed. I immediately moved them under a sink that is never used and STAYS at 72-74. Is there any way you were also having heat spikes?
There was a bit of condensation in the container, so I didn't think they were too dry. We had virtually none hatch, and a few that did had an issue and passed away. We are now left with 2 healthy babies

Our eggs would sweat, start to shrink, and then never hatch. They were also turning that awful brownish tint that your show. I cut a few of the eggs open, and there were fully developed, dead babies inside

. I must mention the eggs were very rubbery and quite difficult to cut through, which is probably why they never emerged . I am willing to bet this is your situation as well. I am still not sure if all of this happened because a the temp spikes, or the vermiculite, but it may be something to think about. I will never use that vermiculite again, as to not have a similar situation happen.
Have any of the babies hatched at all? If so, how are they health wise. You may want to consider cutting open one of the eggs that are dead looking just to see how the neonates look. IMHO your eggs were viable, something just went horribly wrong. I am sorry, I really know how hard that is to go through. P.M. me if you would like, so we can share notes if you would like.
Lisa