Welcome to TFF.
I am indeed sorry to have to be negative in your first post, but you have some problems just waiting to happen here. First, the tank is not large enough for a proper group of Malawi (rift lake) cichlids, so I would strongly suggest you return these before something happens. Depending uppon the species, they can be very aggressive...a third seems to have been the victim already.
Unfortunately the tank is also not large enough for clown loaches, or the Red Tail Shark. This will take some explaining, I'll come back to this, after mentioning something about water parameters.
Freshwater fish species have evolved to function best in very specific environments, and "environment" includes water parameters. These are the hardness (GH is general or total hardness), carbonate hardness (KH, or Alkalinity) and pH, and the three are related. You need to know the GH, KH and pH of your source water, whether tap or well. If on municipal water, check their website where data is sometimes posted, or contact them.
There are two broad groups of fish, soft water species and hard water species; there are some that function somewhere in the middle, though often leaning one way or the other. It is very important to know the species' requirements and ensure you are providing them. Malawi cichlids are hard water, just about the hardest freshwater species. Loaches are soft water. So right off, no matter what you have, one or both of these is likely to be suffering. I'll leave water now and return to space.
Clown loaches are highly social fiish, and must be kept in a small group. Five is about as few as you should have. But here you have another problem, their size; they attain 12 inches (30 cm). That means a group needs a six-foot tank.
The Red Tail Shark needs at least a 4-foot tank, as he will attain 6 inches (15 cm). This can bee a very nasty fish, depending upon individuals, but in the majority of cases they are aggressive, usually to any similar species (like the loaches), and sometimes to certain upper fish.
Given the tank space, and assuming this is your only tank, I would consider re-homing the loaches and the shark. They may seem "OK" now, but I suspect this is a fairly new aquarium and it can take fish a while to settle in to the point where their true nature begins to emerge. Also, the fact that they are not in what they would consider the ideal environment, they are likely under stress which affects them in different ways, usually unseen, but causing internal damage which is permanent.
Byron.
