You do the best you can for them, and then you cross your fingers Lindsay.. I FED Fumagillin B last fall, and I have already lost a couple hives to Nosema.. The sugar cake on the top bars was covered, yellow and brown, and yes, it smelled much like you mention.
How warm is it there? Warm enough to mix 1/1 with Fumagilin and then spray it on the bees?
I am keeping an eye on my bees now. its too cold here to do any spraying or wetting, or even feed a liquid, so the next attempt is going to be mixing the fumagilin with hot water, and using that to make Sugar cakes.. i dont know if it will work, but it is SOMETHING to do to TRY to help when its too cold to do anything else.......
Keeping my fingers crossed for you!