I agree with your assessment, Nerrad.
Whether the tank was originally cycled in the most conservative (prudent) manner initially is a non-issue now. It is cycled. You lost one fish in the interim, for unknown reasons, but that seems to be in the past.
Tetras are schooling fish, but they also establish hierarchies and individual fish play dominant and subservient roles. These are additionally affected by gender, age/size, etc., seasons, etc.
I believe that is what you are observing, and there isn't a whole lot you can do, except by providing physical objects (driftwood, plants) that break lines of sight and allow subdominant individuals to hide from constant bullying. You already have some of that but perhaps you may re-organize and add more, which often shuffles established hierarchies.
Your tank is small and you introduced too many fish - that is sure. Regardless, you need to do frequent water changes, I would say no less than 50% once a week, and not overfeed.
In time, you may consider changing that awful blue substratum (I know that is subjective) and using natural decorations. Another issue is that the grain size of your substratum is too large, allowing uneaten food and feces to accumulate, spoiling water quality. You need to vacuum with water changes.
Good luck!
Whether the tank was originally cycled in the most conservative (prudent) manner initially is a non-issue now. It is cycled. You lost one fish in the interim, for unknown reasons, but that seems to be in the past.
Tetras are schooling fish, but they also establish hierarchies and individual fish play dominant and subservient roles. These are additionally affected by gender, age/size, etc., seasons, etc.
I believe that is what you are observing, and there isn't a whole lot you can do, except by providing physical objects (driftwood, plants) that break lines of sight and allow subdominant individuals to hide from constant bullying. You already have some of that but perhaps you may re-organize and add more, which often shuffles established hierarchies.
Your tank is small and you introduced too many fish - that is sure. Regardless, you need to do frequent water changes, I would say no less than 50% once a week, and not overfeed.
In time, you may consider changing that awful blue substratum (I know that is subjective) and using natural decorations. Another issue is that the grain size of your substratum is too large, allowing uneaten food and feces to accumulate, spoiling water quality. You need to vacuum with water changes.
Good luck!