Can anyone identify these yellow fungus things, and tell me how to battle them?

Eight week old west coast sour diesel from seed. In 70/30 coco perlite. FF big bloom and grow big 600ppm 5.8ph. temp running 65°-79°F rh 49%-51%, six four foot t5 lights.
I noticed this plant has not been performing as well as others of the same seed strain. When I was watering, I noticed these yellow tips just under the soil trying to wrap around the base of the trunk. I dug out, all of them that I could find. it looks like some sort of mushroom.
I've already taken clones from her, and I have other seeds of the strain growing. I would like to save her.

What prevents the fungus from growing? Can I kill the fungus w/o killing my plant? What would you use?

It's known as "yellow houseplant mushrooms" and you they are forming because you are overwatering or you don't have appropriate drainage. That, or the soil you have is some cheap crap where the mushrooms were already present.

Transplant into a new container of soil would be a good start.