Here's a pic of her, she looks bent in the middle, really strange:
http://img.photobucket.com/albums/v400/ ... dbuppy.jpg
Thanks for the link Barney, I did try googling but couldn't find anything remotely close to what she looks like (and behaviour). But to answer the first question - they have a balanced diet, I feed all sorts and only the odd fish is affected - when they're half grown (as she is now). With a tank filled with guppies, if it was contagious or food, I'd expect more to behave like this, not just 3.