Hi and welcome to the forum
It looks like the ovipositor (egg laying tube). When cichlids are ready to breed it pops out. If fish are sick it can come out too and when they are infected with intestinal worms it can become noticeable.
Look for thin red or white hair like things sticking out down there. If there is any hair like things, the fish have round/ thread worms and will need treating.
-----------------------------
The fish not eating properly and rolling over is a concern. Check the water quality for ammonia, nitrite, nitrate and pH. Post the results (in numbers) here.
How long has the tank been set up for?
Do a 75% water change and gravel clean the substrate every day for a week or until the problem has been resolved. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
-----------------------------
Your fish would show more colour if they had a darker substrate and a picture on the backing. And some floating plants would help them too.