Please help! Repotted Orchid Root Going Black

[Singingcrow]

Hi Everyone, I'm new here, and new to orchids.

I bought an orchid a year ago, and in that time the original blooms lasted over two months, the stalk dried up completely, and it grew another two leaves. It never has bloomed again.

This past July, the bottom leaf turned yellow and dropped. Concerned I did some research and concluded it was just an old leaf falling of. But then I went away, had someone take care of my plants, and I'm pretty sure she over watered everything, since my african violet freaked out and dropped almost all of its mature leaves. Anyway, I returned and thought the orchid had survived. That was in mid-August.

Three days ago, I was lightly dusting off the leaves, and one side of it literally lifted from the pot! I also noticed the now most bottom leaf was getting a bumpy texture, and was wilting. So again I did some research and repotted it using a fir bark / charcoal mixture, making sure to soak it over night. There had been one air root, and only one root left within the compost. I put both in the new compost, and this time, chose to use a 4" terracotta pot. By the next morning, the bumpy leaf started to turn yellow.

Today, however, I was just looking at it, sending it loving energy, and noticed the one root that had been in the compost before, is now not as green - more brown, and has a layer of black where it's exposed to the air. I didn't sterilize the roots when I repotted it; I didn't know to. For a temporary measure, I took some shavings of cinnamon and touched the root and the underside of the plant with it.

So now the plant has four very healthy firm leaves (one of which is still growing), a wilted half yellow leaf, and one healthy once was air root in the compost, and another root browning near the base (not the end) with a slight layer of black and a few shavings of cinnamon.

I hope this is enough information to go on.
Please help.?.