Losing Fishes.. Neon Tetras...?

i have 6 neon tetras and now theres only two of them together with 5 pink zebras.... the tetras who died and i killed were losing their color and theyre just laying as they hide behind the aquarium... they dont even eat even if the food was floating beside them but the 2 left were lively and still eating... did i do the right thing for the 4 poor tetras? i just killed one of them and i feel bad... and just in case its neon tetra disease which im not sure of.. what do i do with the 7 remaining fishes in the aquarium? do pink zebras get infected with it too?