With all those points, the cichlas cannot have died unexpectedly. Are the Alestes tetras still doing well? You mentioned your water parameters are fine. What test kit are you using? Have you tested for pH and hardness levels? Most pH test kits are rather inaccurate.
My theory right now is if they indeed ate all the foods rather quickly, their digestive systems were unable to take in all the food thus leading to organ malfunction. To me, this makes sense.
My theory right now is if they indeed ate all the foods rather quickly, their digestive systems were unable to take in all the food thus leading to organ malfunction. To me, this makes sense.