Hey there matute ! Congrats on your first grow ! So basically what I can see from zooming in on your pics is that those "white hairs" are part of the soil itself there are either broken down roots or plant fibers that are mixed in . This is good for the soil, they let in air which the roots need to live, make the soil dry faster which is actually a good thing , and when they break down they will release nutrients which the plant needs. Hope this helps ! 🚀