I don't see anything particularly wrong just from that one picture.
They're africans. A lot of people overstock them to keep agression down. And none of the fish looks really crowded or too big for the tank.
It looks like there is a good bit of algae on the glass.....But that's just aesthetics. Until you test their water parameters, you can't say that anything is really wrong. Heck.....I let algae grow on my decorations and back wall of my aquariums. It scrubs nitrates, and it's actually good for the water parameters. Plus, it give the fish something to nibble on. Am I a bad fishkeeper for allowing algae to grow??? I certainly think not.
I've seen a lot worse. And to me, it looks like there may be nothing wrong here. There could be.....but from that picture, there is no real evidence of poor fishkeeping.