Moldy Soil

Moldy Soil

I just repotted an angel wing begonia that I started from a cutting a few years ago. It's been doing quite well until recently, when it started looking a little peaked. I thought maybe it needed repotting, as these begonias are heavy feeders. Well, when I pulled it out of the old pot, I found mold throughout the old soil. A white, webby-looking mold, as well as some granulated bits of I don't know what (looked like sand, but I don't think it was) and a patch of clear orange slime down in the soil. The plant itself had much less root than I expected, and no big robust roots at all. What is this stuff, and is it hurting my plant? I really love this begonia and I'll be devastated if I lose it. I plan to take some cuttings later today so that I can save something if the whole thing must be scrapped, but I'd rather not scrap the whole thing. I've read that baking soda is a good antifungal- would it work on mold, too? If I mixed some baking soda with water and watered the plant with that, would it kill off the mold and whatever else is in there doing harm?
New to the community

New to the community

yay i finally like my room!

yay i finally like my room!

Plant ID

Plant ID

Sunroot  / Jerusalem artichoke

Sunroot / Jerusalem artichoke

Wish me luck

Wish me luck

Gooseberries

Gooseberries