I know it's been a bit damp around here lately but this is ridiculous. I
just found some mushrooms growing in a container on my third-floor balcony.
Obviously I'm not going to eat them, and this may seem like a dumb question,
but are they going to cause any harm to my Sungold tomato?

There are also some tiny dots on the surface of the soil in that pot but
none of the others. Is this more mushrooms ready to sprout? This picture
is terrible so you might not be able to see them but you can at least see
the other mushrooms. The "dots" are in the white circle.

Pic: http://tinyurl.com/cv4gl

Anything I can do to prevent more of them?

TIA!

LauraJ