in your other hive, were there signs that the queen had been laying? had you been feeding them? if the queen was there and not laying, they may have just moved on. was the hive empty after you installed your packages? did your new bees rob out the old hive?
you may have a problem, but i would try to eliminate the other things that might have gone wrong before worrying about disease, or treatment. hard winters can be killers, so i'd start with examining your winter management and see if there was anything you might have missed. feeding, location, moisture, ventilation (to much or to little), etc.
I appreciate you giving this some deep thought with me, really. Side note: I worked at a medical clinic and there is a saying that goes "When you hear hoof beats, think horses not zebras." Perhaps I have been hearing zebras ;)
To reply to your well thought out Q's: The hive was NOT empty when packages were installed, BUT it was seriously dwindled out. Queen was present, but making no attempts at brood production. They were so acutely diminished I moved them out of a 1 deep/1 shallow combo into a 4 frame nuc ! (w/plenty of honey/pollen...) Their stores had been abundant throughout the winter. They had many FULL frames of honey so I'd made no attempt at feeding, that is until the packages came & I realized what sorry condition they were in so I fed them routinely with the rest. They made little effort to take that syrup. 2 days after that, the queen and her wimpy little cluster of bees were ALL GONE
:shock:. The hive had not been robbed out b-4 or after. There were
curious newcomers hovering about, but no attempts were made to enter and obtain any of the stores that were there. (...another creepy sign of CCD...robbers, wax moths, etc do not not immediately plunder the stricken hive)
I appreciate your thoughts on overwinter management and I HAVE been giving a great deal of thought to it. Screened bottom boards
were used all winter (too much cold wet air?) One of the hives (the first to go) faced south.
.too much wind? I am confident in the feeding routine we used which was to feed heavily in the fall dearth until cold weather came. They had lots of 2-1 syrup put away and capped over (I add a tsp of lemon juice/vinegar/cream of tartar, depending on the week, to prevent crystallization of the syrup) I am likewise happy with their location. Generally east facing, awesome morning sun, on a good hillside for air flow, but protection from the worst of the south and north winds.
All their stores were really quite impressive. As a result the 3 packages I installed literally have multiple full
frames of honey and bee bread with which to start their new lives. And about those little cuties; I just went through them all this afternoon, 85* 8-). Queens are all out, I saw all three ! (...one has barely a dot, I think she might have wiggled when they marked her?!?) :-D There was nice egg pattern in all three hives and lots of fresh comb repairs to the frames they have. Good burr comb here and there, and one hive, which seemed to have way more bees than the others and was given 2 deeps (cuz I have em...) have 3 open queen cells built;
one in the center of a frame and 2 towards the bottom! :? Still, I rejoiced. If my bees at least did something NORMAL like swarm I'd feel a lot better!!! ;) I'll be Keepin' and eye on them, I figure they are just practice cells.
I love you for caring about my buzzers.