Hi and welcome to the forum
Can you post a picture of the entire aquarium?
Can you post a 1 minute video of the fish swimming funny?
Upload videos to YouTube, then copy & paste the link here.
What do you feed the fish and how often do you feed them?
How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before you add it to the tank?
What sort of filter is on the aquarium?
How often and how do you clean the filter?