This orchid looks like my gastrochilus bellinus or my little rynchostylis retusa. My plants growing too slow too! So I understand how you want to help the plant. However, I'm not familiar with your orchid. Black leave can have bacterial infection , but Im not sure.

Is it possible that the new area is colder that the previous? Red / purplish coloring can happen with a temp drop or increasing the light.

None of this looks like infected tissue, Northern Orchid, though I'm going to be watching the all-dark leaf end to make sure . . . I worry that bit of leaf might die, but it might not lead to bigger problems

I wish I knew what the normal growth rate of this plant was, 'cause maybe it's just really slow, but I don't know, and even though it's not a "bright light" plant, our winters here are so dim that I got concerned.

James, it could certainly be colder next to the window, especially at night. Our nights are still down in the mid-40s, and I know the air next to windows is usually cooler than in the rest of the room. It could be getting cold drafts :|

At any rate, I've moved it away from the window spot to a new temporary spot (need to put a nail in the wall to make it a new home), and we'll see what happens.

Well, after putting it back on the wall, all the dark coloring has faded and the leaves are just green again (I think it faded in a little over a week, but I wasn't paying close attention). So it probably wasn't damaged, but I wish I knew if the darkening meant "this is a good bright level" or "this is too much."

Thank you for update! Good, your little orchid is healthy! So it wasn't sunburn but environmental change of leave's color.

I've never grown this plant. On my mounts on cork I put the moss above the roots so it gets a prolonged drip after it's daily waterings. But this species may need its roots to be buried in the moss.