If shes been fine before then i wouldnt put it down to her breed, there will be a reason, just need to work out what it is shes trying to communicate.
Are either of the other 2 a new addition to the family?
If its a stress behaviour then feliway may be helpful.
Tesco sell an ultra fine clumping litter called sophisticat choice, its like sand
![Grin ;D](https://www.purrsinourhearts.co.uk/Smileys/purrs smilies/grin.gif)
What are you cleaning the soiled areas with?