fish keeping can be so difficult and frustrating, especially at the start. i’m sure most people in this reddits first tank was a flop. My advice would be to get rid of the plastic decorations that can have sharp edges that could be causing small abrasions. I would also monitor feeding time making sure not to over feed and not to let food sit in the tank. Personally I would focus on stocking this tank with plants before trying to get the fish population established. To do this i would put in some gravel designed to sustain plants and get a plant light for them. If this is not an option try to get some soft fake plants. Additionally, frequently monitor water parameters to find any potential causes of loss (make sure you used a good testing kit because the strips tend not to work as well.) . If you do happen to lose a lot more fish I would try to under-stock this tank with smaller more beginner friendly fish. Like a beta with a school of corydora. There’s lots of better resources than reddit out there for fish info, youtube videos helped me a lot in the beginning when I didn’t know what I was looking for.