This is the second Bhut with the fungus or....

I can't quite tell, but I think it is just a mineral salt residue from when the soil was once quite wet. Otherwise, if it is a fungus it looks like things are getting dry on top, which will take care of it. Those plants are beyond the point where I would worry about a little surface fungus getting them anyhow. Looks quite happy. Cheers!

I agree that these seedlings are beyond worrying about fungus.

The fungus, if such it is, came with the soil no doubt. Pics aren't clear enough for me
to tell if its salt build-up. In nature, plants co-exist with tons of microbes and fungus,
so the presence of fungus really only indicates that conditions are right for fungus...
that, of course, can mean that things are consistently moist/damp. In some soils, this
poses a significant problem, but your plants seem well-established.

Josh