litter box rebellion

WE addopted a second adult cat. The new cat his for three months and all was fine. The timid one would spit at the other if they ever crossed paths. Once Nugget came out of hiding made the mistake of going to one litter box. Spice immediately rebelled and started pooping on the floor. Even though we immediately went back to two boxes, Spice still refuses the box for poop!

I've even placed Spice's box in the her preferred 'poop spot' with no effect on the behavior - she simply moved over 2 feet to 'do it'

What else can I do?

Add another box and another- two cats, three litter boxes is best. Put the boxes in as private of a place as you can that helps also. If kitty still is pooping outside the box after you have added the new boxes, then a vet visit is in order. Sometimes stress can cause a kitty's immune sytem to go haywire. So a vet check is a good thing to do.