sudden fish death

Question
i have a 2ft by 1ft sized aquarium.There are 6 different species of gold,1 loach,1 crocodile fish,3 widows,9 zebras,2 lillies,1 battice.My 4 tetras,1 redtail shark & 1 zebra died suddenly.There was no change of water also.I have a sponge filter with fake as well as live plants in plenty with 2 cfl lights.My shark was completely discoloured.Plz help.:((

Answer
Dear Shuvadeep,
In your question it is not clear that how many fishes have died (6 different species of gold,1 loach,1 crocodile fish,3 widows,9 zebras,2 lillies,1 battice.My 4 tetras,1 redtail shark & 1 zebra) or only (1 zebra). It is also important for me to know that how long you didn't change your aquarium water and why ? I'm waiting for your detailed reply. Thanks. Good Luck.

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