Guppies bent to the side dieing?

[fishlover18]

They are in a planted tank. sometimes eat the sand. It is a ten gallon and is filtered and kept at a bit warmer than room temperature. i had 4 males 1 female and 2 guppy fry. Within the last two days i noticed that one had been curved like a boomerang and having difficulty swimming, he died along with a younger guppy this morning, now another is doing the same thing.I have noticed they also eat the sand, could this bee the reason?I was going to add more guppies and maybe a dwarf frog but now i am afraid they will die too. Please help

 

[TraceyB4602]

It your tank cycled? What are the parameters?

 

[fishlover18]

yes. i did a fishless cycle and they have been living in it since februrary.