If you wound up with a cup of that stuff, I'd say you have a mineral problem. What exactly do you use for your plants' media?
Typical sand/peat mix, top dressing of finely chopped LFS. The original is in peat/sand/perlite. To be fair, a couple of the transplanted seedlings had bits of the fuzz on them that I didn't know how to remove without the aid of a microscope. Seedlings were only a couple millimeters across at the most. They're dead now, I put them outside hoping the lower humidity would dry out the fuzz, but temps shot up into the 80's and RH way below 30%. That's okay, there were only 5-7 seedlings, I still have maybe 20 or so still in the original pot.
Grand Hotel... always the same. People come, people go. Nothing ever happens.