Now, some may call me crazy. :shock: The hipsters may call me a doofus. But just as I sometimes pick up the yellow pages every now and then, I also feel that every little beekeeping problem may not be solved by playing twenty questions about every dead hive out there. Sometimes, old school still works the best. And just like before this crazy thing called the computer took over most people's lives, and everyone instantly became "kewl", I'll suggest that perhaps the best thing you can do is seek some advice from a local "old-timer" (Just ask if they use the yellow pages....that makes them an old timers ;) ) and see if they can take a look at your hive. They may be able to give you some tips on the local weather conditions, etc. Nothing beats actually looking at your hive to pinpoint the problems.
Knowing your brood production last fall, when was the last time you seen brood, and many other points would help. Is there brood now? Are they starving out, or are they just dwindling out with a failed queen? Are the bees scattered to the four corners of the hive, which may indicate T-mites? Are there dead bees outside in front of the hive that could indicate pesticides? So many questions. You mention old equipment, but AFB to the point it would kill a hive, would easily be recognized. The fumagilin, is not needed, unless you see signs of dysentery, which by know would be obvious.
Do you have or know anyone who could take a look at it?