Yeah, that looks like fungus. Usually what I do is don't mist the leaves, and I don't even let rain hit it since it appears that it spreads the spores more easily. I've ran into this issue from time to time and what I do is unless it's a nasty case, I remove the larger leaves that are infected and that'll help cirrculate more air and sunlight and keep the foliage dry. As for as treatment, I use a Neem oil insecticide/funguscide and spray it as per directions, usually every two weeks or so.
So the solution seems to be, keep foliage dry and well ventilated...just water from the bottom.
Let me know how things progress.