Black mold

[markr]

What you've described sounds like black sooty mold - sort of a black powdery substance on the bottom and edges of leaves? It grows on honey dew secretions from the leaves and in itself isn't very dangerous. Excessive honey dew though is often a sign of insect pests, so check carefully for that.
To get rid of the mold (assuming that is what it is), just rub with alcohol. Keep your orchids clean and it shouldn't come back.

I can't see any mold in the pictures though - if you are referring to the green stuff on the potting media, that's just algae. It's harmless unless it completely takes over your potting media.

From the pictures, it doesn't look like there is any need to repot - the moss looks fresh. It's wet but I'm assuming that is because you've just watered it within the last day or two. It should dry out in about a week.

[alannanoelle]

Yes, I cleaned off pretty much all of the black mold, and it hasn't come back so far. As far as the moss goes, I am assuming it just got watered at the store before I bought it. I soaked up some of the excess moisture last night, but it seems like it is okay. I'm monitoring it closely though! Thanks for the advice!

[Leisurely]

Your plant, at some time, probably had aphids or mealy bugs. Both secrete a residue that is food for mold. I think if you just clean the leaf with a mild soapy solution, you will be fine. You might also replace the top layer of sphagnum. It is turning green because of algae growth which is common on moss that stays moist. It is not harmful to the plant if you want to leave the moss alone.

I have had mealy bugs on Phal flowers before and any leaf directly under the dripping of the residue they secrete got mold on it.