I do not have any known buckfast-esqe lineage, but i do have a mixed bag of those with good stores and those with little who are being fed.
Fair comment... However, if, for arguments sake, you had(/have) an apiary of let's say 10 colonies; all overwintered well, ostensibly disease free, with low varroa loads, and all with good brood/stores, and expanding rapidly, and then, after an admittedly wintry 2-week snap, say 6 our of the 10 were in good condition (albeit not storing) but 4 had really significantly regressed (queen off-lay; excessive consumption vs. income), would you not start to try and find a correlation ?
There must be a reason; you can't just write it off.
Of course, in every case, it could be any number of things, but my empirical observation is only that, in my case, those most affected are those a) of recent Buckfast (as opposed to locally adapted) lineage, and b) in the main, in poly-hives.
My personal conclusion, based on the limited evidence, is that these had 1) expanded too quickly, too early, and 2) were unable to react quickly/appropriately to the conditions.
For my part, I won't be using their genetic material to rear new queens. I'm also coming to detest poly. That's another topic (i.e. Thermal Theory = Emperors New Clothes).
More widely, it has to be said that, in general, over the last two years, all my mongrels in wood have been bombproof and could be left alone, and all my colonies from bought-in progeny, kept in poly-hives, need to be constantly nursed to keep them alive. It's mid-May, for eff's sake. I shouldn't need to be trying to keep my bees alive. I steadfastly refuse to feed my bees at this time of year; though one did get a frame of stores from another colony yesterday to help it pick up. Weird times.
Oh, on and every measure, from temperament to yields etc... my best colony by far is still a mongrel colony (originally of Carniolan lineage, going way, way back to 2013). These are babes, which I have recently split, with both parts of the split doing well. Same apiary as the duffers.
Anyway, I'm straying off topic ... and it has to be said that, as of yesterday, many (except for the babes, above) were a bit pissy; irrespective of whether they were regressing colonies or not. I think it is fair to say that, at present, the forage (and, by extension, the weather) are triggering tetchy behaviours.
