I think you've finally met people who treat fish like pets and love them, and you just don't know how to deal yet. we're aware that most people could care less about fish and aren't going to take this advice, but better to give it than to give up.

The truth is, you're poisoning these fish. Their bodies are being chemically burned as I type. Fish actually are not meant to live in their own waste. Naturally there are bacteria that coexist with fish and consume the chemicals given off in their waste and give off less harmful waste. When the bacteria are non-existant, the fish die. Its slow and painful for the fish. Cycling established that bacteria in a tank, but with so many fish in such a small tank you just can't grow enough bacteria to compensate for the waste load.

I can tell you by the pictures that it looks like the small fish in the 10 gallon are suffering ammonia poisoning. You need to get a test kit if you don't have one already. Every day you should be testing the water. I'm sure you'll find for the first few weeks that you should be changing the water almost daily or every other day. You might even see physical signs of healing when the ammonia is taken care of (fish often turn black while healing wherever their skin was burned from ammonia).

As far as overfeeding goes, you're not overfeeding. Feeding suggestions for tank owners are made so the owners have the least maintenance. Less food = less waste. To me, its cruelty. Starve your fish so that the ammonia levels don't get out of control. That's exactly what a pinch a day per fish will get you. Its what people have to do when they don't have time or knowledge of proper care. Granted the choice for the fish is either: be hungry all the time or be constantly poisoned by my water. No wins for the fish in either situation.