First thing, obsessed with fish--welcome to Tropical Fish Keeping forum. And also to the hobby.
I too am in agreement with the other members' suggestions. Before getting to specifics, I'll mention our fish profiles, under the second heading from the left in the blue bar across the top of the page. All the fish mentioned so far are in our profiles, with data on their needs respecting numbers, tank sizes, compatibility issues, etc. Please have a read of those, as it will help you to understand what we are getting at.
I am going to take a moment to pick up on your comment that the fish are all healthy, happy and showing no aggression in the 10g. Fish are designed by nature through natural evolution to live in very specific environments, and this is clearly more significant with fish than with almost any other animal. Their aquatic world is quite unique, compared to terrestrial animals; fish have much less adaptability because of this. They have inherent needs, which if not met will cause stress which is not observable by us until it is almost too late. Sometimes increased aggression results from this stress, but at other times fish may be the exact opposite and become more passive than nature intended. Either situation leads to weakening health and the fish never live to their expected lifespans.
We as aquarists cannot change a fish's physiology. The only way to ensure they are healthy is by providing them with the closest environment to their natural one. And environment here refers to many things: water parameters (GH, pH and temperature), water flow (some fish need currents, some do not), appropriate decor (wood, rock, plants, sand/gravel substrate, etc), adequate numbers for the species and sufficient space for this, and suitable tankmates. Any one of these if not close to the species' requirement will cause stress, and stress is the direct cause of almost all disease in fish.
I hope this explains what we are all getting at. We all had to learn this, often sadly through error which means sick and dying fish. A hard lesson, but one that must be understood.