Fish Dying!!!

Question
My last female just died a few minutes ago.  Well, I bought a 1 gallon tank.  It came with decorations, a filter, and a bubbler, and gravel.  I set it up and waited 24 hours before putting the fish in.  I fed them every day.  I've got a light that I turn on and off to keep the temperature regular.  I got the fish from WalMart so could it be that they were sick before I got them?
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-----Question-----
About a week ago I bought 8 fish.  I got a sucker fish, betta fish(put him in his own tank), 4 guppies(2 male & 2 female), and 2 neon tetras.  The first to go were the 2 tetras.  Then the betta died.  A few days later 2 of my guppies died.  Now I'm left with a male and female guppy and the sucker fish.  The male has like a whitish form on his mouth.  The female has a little white patch under her top fin.  Do you have any clue why my fish are dying?
-----Answer-----
I may know , but you werrnt specific enough.  I assume you have a new tank that wasnt cycled.  The hgh ammonia levels are probably killing the fish.  

Heres how to cycle a tank

Set up the tank putting in decor.  and gravel too
install filter hearet and bubbler
let it run for 6 weeks or so this allows bacteria to grow
i would start out with 2 guppys 2 platties and 2 swordtails

as to the betta im stumped.  try letting his water set for a week or so too

Hope this help and im welcome to replies,
paul

ps sorry about the grammar im doing hw!

Answer
One week is too short for the tank to cycle.  Im so sorry about your fish.  

Are you sure it is a 1 gallon.  If it is the fish either died from the high ammonia from the low cycle time or ich from being too crowded.  

If you meant a 10 gallon it is still a bit small for all the fish.  

Best of luck,

Paul Hotaling