I have 3 cats. 2 girls around 2 years (Selene and Piper) old and 1 boy around 10 (Nikki). We determined recently the boy must have an allergy to one of the canned foods we give him. Once we figured it out he got better after a few days. While he was having issues, one symptom was semi-loose stools which stunk.
We have 4 litter boxes. 1 in the bedroom which is usually his main box (though Piper uses it too). 1 in the computer room which rarely gets used, though Nikki and Piper occasionally do. The other 2 are in the craft room and both girls use those and occasionally he does too.
The problem started when Nikki had his latest issue. He used one of the boxes in the craft room which stunk. Ever since then Selene has not pooped in any litter box. I have tried scooping the boxes once, even twice a day, and recently also tried adding litter box deoderizing powder. She would still poop all around the box but not in it. So I moved some cardboard boxes around the sides and back so there’s no room to go outside the box, now she continues to poop in front of the box instead. I put a large litter-catching mat down and she poops on that at this point, so at least she isn’t hitting the carpet. I put in a new litter box. This one was smaller than before with a half lid hoping this would stop the boy from going in the box (the girls are small, around 5 lb where he is around 15). But he still used the box anyway and the girl continues to go outside the box. So I swapped out the box yet again for another new one … this one larger but no lid … thinking that the increased real estate maybe would have her thinking that if any cat used the box before I could get around to scooping it, that it wouldn’t feel like a single poop was filing the box.
I completely change the litter out of all boxes once a week and just recently she pooped again on the floor before ANY cat used the box at all. So a new box, with fresh litter, and none of them had used it yet.