Thanks for the opinions.
These were splits of new packages, in new hives. Both these hives had two brood breaks, one on install and the other when they were split. I didn't think mites would be an issue and didn't look.
The bees were scattered through out the hive, looked for the queens but didn't search or find.
They were package bees out of California, probably some of those 'dime a dozen' queens. The splits were made with swarm cells out of the same stuff.
I had a lot of bitter cold/ bright sunshiny days. The hives weren't wrapped, but the sun still must of warmed them some. Could they broke cluster and got stranded?
Today is supposed to be warm enough to do a check on my living hives. Maybe that'll shed some light on my dead outs.