stoped using litter box

Question
I have two cats, one male one female. They are in good health and are indoors all the time. One started to poop on the floor, but will use the litter box to pee. Then the other one started to do the same thing. We change the litter box two times a day morning and evening. Changed brand and that didn't help.Otherwise they are good healthy cats. Thanks for any help.

Answer
Randy,

Are they neutered & spayed?  How old are they?

Litter box habits usually change for either medical or behavioral reasons.  The cats may appear to be healthy, but there may be problems which are less obvious.  Once one cat begins to miss, the other will smell what is going on and may follow suit.

Lets look at medical possibilities.  A urinary tract infection (UTI) may be hard to detect without a veterinary examination. Another possibility is that the anal glands on one or another may have been impacted. Once they are expressed the problem often goes away.

Every time a cat has missed the litter box, the area needs to be cleaned up with an enzyme based product specifically for cat stains and cat odors (available at most pet supermarkets).

It is also possible the original issue is long gone, but by changing brands or type of cat litter, the cats are not happy with the change and will tend not to use the litter as much. Another possibility is that the "pecking order" for litter pans has changed and one of the cats is not letting the other one use it. Have you tried a second litter pan a bit away form the original?

Please let me know about some of the above.

Best regards... Norm.