Help sick molly!

[tlfphoto]

One of my marbled mollies in my 55gal tank started shaking a couple of days ago and now she is swimming with her head down and will not level out. It is like she is swimming doing a hand stand. She eats and the other fish have no signs of this.
Please help someeone.
Tommy

 

[Kurty]

:-[ :-[ :-[ I LOVE MOLLIES TOO refer to dead mollies lots of helpful info there SORRY BOUT YOUR SICK MOLLY :-[ :-[ :-[

 

[luvfishies]

I don't know much about mollies as I don't keep them, but is there any salt in the tank? I've read where Mollies kept with too little salt (they prefer brackish to full blown salt water...not an option in a commumity setting) behave like this.

anyone else have any idea?