Why has my cat has started going out of the box?

[bloodybill]

I've been cleaning the boxes everyday, and I've only had her poop out of the box 2x in the last month. They all use the great big box, and will only occasionally use the other ones.

One of my cats has a very disgusting habit. He rolls around in the litter box. It's so gross, I have to wash my hands after I pet the little beast.