The cichlid on the left in the picture is a lombardoi (kennyi). The fish on the right looks like a demasoni.
Both need water with a GH around 300ppm and a pH around 7.6-8.0. Unfortunately this won't work for tetras.
The lombardoi will also kill tetras and most other fish when it matures. It looks like a female so should be less of an issue compared to a male but they are extremely aggressive when mature.
The demasoni could be getting bullied or have an illness. It looks ok physically but need a video to see how it is breathing. You can upload videos to YouTube, then copy & paste the link here.
If you film the fish with a mobile phone, hold the phone horizontally so the footage fills the entire screen. Take about 1 minute of footage and post some pictures of the entire tank. The cichlids need lots of hiding places.
Is the fish eating?
What does its poop look like?