HELP! Black Spots/Yellowing leaf (Indoors Dendro)

[Jkelee]

Hello Again,

I have had this Dendro for only about 2 months or so, from Lowes. I keep it in the house, on the counter, not Direct light at all, so no sunburn possible. I only water the media, not the leaves, so can't be water sitting on leaves. About every 2 weeks, a leaf will be lying on my counter, looking like this one.

So now I'm stumped. I've looked and looked for the same pics, and all I found was Rungus, and sunburn. I can't be sunburn, so is it A Fungus?? Plz help!

Thank you!