White stuff in my soil

Define "White stuff" if it is white-styofoamish/pumic style rocks, that is the perlite and keeps your soil aerated and from compacting. If you are seeing fuzzy white mold, what kind of soil are you using? Roots Organics Lush and other will come with mycorrhizae which on a old bag, can look like white mold.

The most common reason mold starts growing is if you are overwatering your plants. When growing in soil, you want to make sure the top inch of soil dries out before you water your plant again. If you water more often, you make a better place for mold to grow and you can also overwater your plant. If you already have mold growing, take a spoon and scrape off all the mold, being careful to not let it touch any new parts of the soil if possible. Then lightly mist the whole area with a mixture of half vinegar and half water. You don't want to get the soil wet, just mist the top part of the soil with this solution. The vinegar can hurt your plant's new roots so be careful to use as little as possible. You may want to repeat the vinegar-water mistings once a day for two or three days. This should kill any mold that remained after you scraped the visible parts off.

Is it not the perlite keep that in mate