Bee North - good question. Yes I opened several of the unhatched queen cells. Each cell had a dead queen.
Florida - I did not move the splits 2 miles. I have been relying on anti-robbing screens instead. In each hive that didn't hatch a queen, I found rather small patches of bees, much less than I had originally installed, as well as significant patches of un-hatched brood. For comparison, the successful splits still had a large qty of bees, about the same as I had originally installed.
All failed splits had enough stores remaining. 3 had gone LW. It seems that I've finally got a handle on robbing at least. ...
I am of the opinion (now) that I got large numbers of field bees in these failed splits, and that the field bees returned to the parent hive, leaving not enough bees to keep the QC and Brood warm enough.
Currently I'm in the process of testing this theory with 7 new splits - for which, I purchased Queen Excluders, moved all (and only) brood above the QE for 24 hrs, then pulled only those frames/boxes - which would contain, almost exclusively, nurse bees. My 7-day inspection (last friday) showed lots of capped QC'S, and lots of bees.
My "check date" for this latest round of 7 is: April 19th. I'm hoping that my split success rate improves now. ... we shall see