hello, I have seen fuzzy yellow fungus in some of my clay pots. I suspect it is in the ones that do not dry out 100% between waterings but I could be wrong. The soil will smell fungy, and there will be what looks like tiny patches of yellow cottonwool, but it will have little 1mm tiny yellow balls in them. They are not spider eggs. It is some sort of fungus. The balls are amazingly hard. The plants growing in these pots do not do so well. What is it and how do I stop it from coming back (copper, zinc, systemic, something that will not kill a cactus please.) Thanks.