Is the fish in first photo alive? He is probably either sick or dead and the other fish are picking on him.
First things first is if he is alive, move him to a quarantine tank to separate him from the other fish so they don’t kill him.
if you don’t have another tank, that is okay, just get a good sized tub (like Rubbermaid or sterilite) and fill it with water, toss a sponge filter in there and add a double dose of prime and stress coat. I would also add a mild dose of salt and a few plants to make him more comfortable. Also add a heater. Acclimate him in. Keep it dark so he doesn’t get stressed.
next thing, your tank is way overstocked. That tank is way to small for those types of cichlids and they are so crowded they are picking on eachother. I would get a second tub and do the same as the first and move some of the other fish into that one so they quit picking on eachother so much.
if the fish is dead, then remove him from the tank and dispose of body so ammonia doesn’t build up in tank. Do a large waterchange and add some prime and stress coat. You’ll probably either need to rehome a couple of the fish or invest in a larger tank.
If a fish is dead, then you should remove it immediately so it doesn’t pollute the water.
What are your water parameters? This is extremely important. If you don’t know, I would really recommend getting an API master test kit
The tank is definitely to small. I would recommend getting a larger tank with a sand substrate, proper filtration and plenty of hiding places to break up the tension between the cichlids so they are less aggressive.
If your tank is not cycled, then you probably have quite a large ammonia build up in the tank. ammonia can easily kill fish or stress them out enough to lower their immune system which makes them susceptible to disease.
To lower ammonia, do a couple small waterchanges and add some Seachem Prime.