Black Spots on Phal

[scy]

Hi,

I received this no id phal as a xmas gift and noticed it had a few black spots under one of the leaves. I ignored it and hoped it was not a big deal but now I noticed it spread to the underside of the leaf on top of it.

What is it and what should I do? Please note that I took this photo with my cell phone and it doesn't accurately reflect the color of the actual leaf. The leaves are dark green from lack of light. I've opened up my sheer curtain to give them more light. Thanks in advance for the advice!

Susan