Black on feathers

I've heard of stress bars. But these aren't bars.
Rico came to us in February and his diet wasn't very good at his last home. It wasn't the worst, either though. But nonetheless these black areas of feathers were there and I figured a good diet would turn it around. Now I'm not sure, but I think some many be growing out with some black areas, as well.
What are they?

Here is a pic. I hope.

There's several possibilities, it could be due to his diet, if that's the case, his new feathers shouldn't be coming in with spots. It could be a symptom of liver damage, or psittacosis. I don't want to cause you undue concern but it doesn't look like stress bars or a result of over preening to me. I would have him checked out by an Av Vet, just to be safe. Here's a couple of links to recent discussions on the topic;

http://www.parrotforums.com/conures/47484-black-feathers-conure.html?highlight=Black+spots+feathers

http://www.parrotforums.com/conures/45310-black-tips-feathers.html?highlight=Black+spots+feathers

Oh, if it's liver, I've actually just done a detox, and will be buying milk thistle, to help support both my birds liver! That's actually better news then, because I was stumped.
He was fed a lot of fat in his last home, so I expect his liver to take a little to settle.
They said Doritos and pork was his favourite.
They also said he didn't like toys...
I will read more, thank you very much for answering and giving me material!

My GCC Flick came with huge black areas on her feathers, so much so that her back had a very scalloped appearance, with more black than green. Her diet had been pretty good by most peoples standards, pellets and fruit. She tested negative for Psittacosis, polyoma, and pbfd, and the vet said there was nothing wrong. She just just finishing up her first molt, and molted in all nice healthy feathers. At first I thought she was molting in spots, but as it turns out, she just molted really slooooooowly.

My suggestion is to take the bird to see a vet, but don't be too frustrated if they don't ind anything. I suggest taking a close up picture of some part of the body, most likely the flight feathers. You can use the picture to compare, and see if NEW spots are coming, or it simply the old ones are staying. That may give you peace of mind, and may give the vet some insight as well. Good luck!

My conures feathers looked much worse than that when in first got him. It took 2 moults for the dark spots and stress bars to fully leave. They are completely gone. He was on a crappy diet as well. But after over a year and a half of healthy eating, sunshine and fresh air they're completely gone. So it could take a while.