[pcord]

I have heard it said many times that cold does not kill bees and I believe that. That being said, if the bees did not have the right layout of stores and the ability to get to them, then they could have died of starvation even with lots of honey. There could have been excess moisture in the hive which dripped on the cluster and killed it. There are also a bunch of other things that could have caused what was a "strong" hive to die off.

You should look into the mountain camp method of feeding. Search for the threads. You do not need to expose the bees to the cold. Just get food on them NOW! If you break the seal between the inner cover the top super, you should then be able to slide a piece of newspaper in between the two. Cover all but the last 10th of the top of the super with the sheet. Once on, pull the inner cover off, put an empty super on top of the paper and dump in sugar on top of the paper. You can mist it with water if you want. Put the inner cover on top and then the outer cover. Do the search for more details but the beauty of this method is the bees don't need to break cluster to get to the food.

You can also try to pull the full honey stores from the dead hive. The advantage is you're feeding them honey. The disadvantage is that it won't absorb excess moisture like the sugar will.

 

[pcord]

Personal opinion here, but I wouldn't spray the sugar too much. Maybe just the leading edge since that's where the bees will start in on it. One of the big benefits is that the sugar will absorb excess moisture in the hive. Wet it too much and you diminish that ability. From what you say that there was mold down by the dead bees, it sounds like you may have had too much moisture dripping on the cluster. Your hives are tilted forward at least 1/4 bubble on a level, right?

On another note, add the sugar NOW! Don't wait for a calm day. Don't wait for a warm day.