part of the problem may be due to aggression/bullying in a tank that small they don't really have anywhere to get away to if they are being chased.
i have a 4ft long 37gal tank with 14 girls in it, plus lots of planting (there are also 7 khuli loaches and a bristlenose, but they add no problems to the aggression and not much to the bioload) i occasionally see one chase and nip another, but the one being chased can swim away and hide without any problems
also bear in mind that recommended minimum tank size for small fish is 1 inch of fish per gal, which would indicate you need an absolute minimum of 4 gal, and due to the aggression issues, i would personally go for much bigger.
as pheonix has said, your ammonia indicates a problem too. do an immediate 50% water change on the tank as this will be causing serious stress to your fish. this level of ammonia on a filtered tank is most likely due to overstocking or not cycling properly before adding fish. (add some duckweed to the top of the tank as a temporary measure, this will suck up the ammonia as food)