This could mean that there is too much moisture for the plant itself.That fuzzy thing needs much more moisture than marihuana plants preffer,think about the lower parts of the pot than.I think you have to let dry a little more.And may be compost those leaves somewhere else,not directly in the pot when you grow.People do that with the leaves but I don't know,i wouldn't leave them there.....
Reminds me of when I transplanted my first promix hp coco. Bone white silky hairs shocked through the coir. I thought I had a problem for a sec. Then I remembered the promix comes with mycorrhizae and I just had a very healthy colony going lol