So last week I went out to water my tomatoes, and one plant had this weird offwhite gunk on top of the soil around the plant. I poked at it a bit and was completely confused. There was also a lot of slug slime around the area, so I thought it might have something weird to do with slugs.

And then suddenly the gunk was gone the next day.

And then yesterday there was more of the stuff, and slug slime trails again. and today I went out and the gunk had puffed up to about 10X the size it was before, and was dry and looked like some kind of mold or fungus. So I am assuming the stuff was spores--does this sound likely? The question is, where did it come from, and what should I do about it, and what damage might it do???????? I haven't seen anything like it around any of my other tomato plants or peppers or anything growing in my garden.