I used to have these plants growing in my dorm room. I needed to add some more herbs to my collection, so I dug up most of the previous plants, took the soil from the pots, and mixed it with home depot potting soil. I watered them like normal and found this white stuff growing all over the top of the soil and on the pots. I'm guessing mold but I have no experience with plants so I figured I'd ask first.
I'm wondering what this white stuff is, if there's a way to get rid of it, and what's the best way to prevent it from growing again?