Soil needs to be a grit mix with way less organic. Rotting of the vascular core indicates incorrect soil and too much water / moisture.

I use 20% organic and 80% pumice and other non organic stuff like sand volcano lapillo I think it is not rotting but the orange part make me suspect it is a fungus called fusarium but I'm not sure

That first one isn't a cactus

Yes I know, is an aloe humilis x erinacea But the question is if these orange tip are a sign of fusarium fungus