Hello
I had CBPV a few years ago in a couple of colonies. It doesn't come on like that overnight. If it was CBPV then alot of the dead bees would be black and shiny with very little hair - I don't think your first photos show that. You'd notice bees dying around the frame lugs and bees that are so lethargic they don't move down when smoked. They tremble, crawl about slowly and generally don't look right. They die off inside the hive and are dragged out by the other bees, hence dead bees on the floor and outside the entrance.
You have a picture there of bees bearding on the front of the hive. It may be that they were bearding when the heavens opened and they got wet, cold and died. It could be that they're needing more ventilation - you say they're on a solid floor, an OMF would be better for ventilation (and mite control).
If they are fine now I would definetly rule out CBPV. Still can't rule out poisoning. I don't suppose you took samples?
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