Not sure what I'm seeing.
Keep meditating as it usually strengthens your abilities.
If you are seeing full rainbow auras around people then at that point you can trust what you see. People that can see full auras will tell you that when a person has an area that is weak and causing them problems that part of the aura will project as kind of muddy brown or fuzzy black. But if you are not yet seeing full auras, I wouldn't worry about that assuming that you are seeing your aura.
I do, however, have some experience with ghosts and rid myself of a spirit attachment a couple years back. It sounds like this could be an explanation for what you are seeing and working through. First off we all have to realize and accept that ghosts are everywhere. And the vast majority of them are harmless. They are particularly attracted to empaths. Because of who we are and our natural higher vibration, the ghosts are very drawn to us.
I do not usually see ghosts, my ability is that I can hear them. However, on the occasions where I have seen ghosts they have always been shadowy black and in different shapes and sizes. I usually see them as blobs and not in any type of body outline. My daughter is an empath and normally sees ghosts in human shape and she tells me that they mostly appear as shadowy. Most present that way. From what I hear from others, ghosts normally only present with great detail when they have passed recently.
In getting back to your situation, I had something black on my back not too long ago. I couldn't see it in the mirror. But when someone dropped something at my house I whipped around really fast and saw this black object that was attached to my back and almost looked like a black cape. I saw it at various times for about a week and nothing since. I think this may be what you are seeing. With my hearing and general empath radar I feel certain ghosts come hang around me for a few days regularly. And then they usually move on. When it gets on my nerves I ask them to leave and they usually comply. I believe the same thing happened with that black cape-like thing on my back as it disappeared about a week later.
As an empath you already know that you pick up on living human emotions. But you also can pick up on ghost emotions as well. The thing about earth-bound ghosts is that they are here because they have not crossed over yet. And they are usually here due to confusion, unfinished business in their former life, or guilt/strong emotional attachments that keep them here. If you ever watch one of those legitimate ghost hunter tv shows where the empath or medium walks into a haunted house and feels pressure on their chest and picks up on anger, sadness etc... It's exactly like that. While humans have a range of emotions, ghosts normally exhibit the emotions that are keeping them bound to the earth-plane. For example, if someone died from a drug overdose, their ghost may present with feelings of sadness and regret.
If I am a correct and you have a ghost keeping close to you, I would just test it out by trying to clear your mind and see if you can pick up any emotions from the entity. If you are noticing unusual moodiness or ill feelings yourself, that may also be you reacting to ghost emotions. As an empath we are always asking ourselves "is this emotion mine?" So if you all of a sudden are feeling angry for no reason, a lot of times our brains accept that as "our own feelings" and we just go with it and feel anxious and angry. But as an empath progresses, we learn to discern what is not ours and recognize it as incoming emotions from others. This is the same with ghost emotional energy that you may be picking up. You'll feel it as your own. But you can block that or just ask the ghost to leave. Protections stones also work well to keep ghosts from impacting your energy field.
Let me know if you feel that this info. helps. And if you are feeling a lot of fatigue lately, let me know on that as well as that is an off-shoot of this topic.