guppy in distress (with clamped tail)

[monka]

hi

I noticed yesterday that the smallest guppys tail is clamped shut and she is having problems swimming. she didnt eat much today and is now on the bottom of my tank on the gravel having great difficulty keeping above that level.

i did a 20% water change yesterday and again today. All the other fish look fine. i have only had these fish for a week and a half.

My tank is 12 gallons and has been cycled for 5 weeks before i put fish in it. i have 3 guppies and 2 platys.


Hope someone can help me please.
Thanks