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My B.Smithi has developed this bald spot with this weird almost fungus looking thing on it's abdomen. I keep the enclosure very dry, she is also not a hair kicker.
It seems to me that it's only the "fluffy" border of the hair kicking zone: when the hairs are almost detached but not entierly...
My smithi, boehmei and klaasi do that even if they don't kick hair usually. Kind of a pre- premolt thing (!).
It's maybe related to some stress due to the fact they happen to be wandering restless a little bit in their enclosure for a specific period of time (don't know why)...
My juvi b.smithi is the same, not a big kicker but in premolt she will lay web down in her enclosure and kick hairs on it. Its a defence mechanism to warn off predators when they are molting. Also the fluffy bits are what nicolas said, just loose hairs that havent come off properly yet. I wouldnt worry.