A lot of very good detailed questions. The dead out last summer was mites and the dead out was the same hive that was poisoned last spring. Thank you ID, he figured it was seven dust.
So now on to the today deadout. No sigh of mite frass, hive last treatment OAV was December broodless stage, four treatments total, July August sept dec. There is a very small amount of honey in the hive, outer frame, bees died on frames 3 and four inwhich there was zero honey and previous 3 weeks was cluster temps so moving honey not possible. Zero brood. Hive did have mold on top frame in the top nuc, last week of December which alerted me to an issue, small number of bees. Bees died tight clustered 6 inch diameter on both frames 3 & 4. Dead out was new blood, 2019, carniolan, solid black queen.
Of interest, another hive only inches away has 3.5 frames of honey in a ten frame single deep Langstroth with 5 frames of bees and a small patch of brood.
I think I answered all your questions, Phil. If not, let me know.
Health to your bees.