Sick Cats?

I would take the poop to your vet and have them run a test to see if there is worms. One of my cats somehow got roundworms, and to let me know he started pooping in front of the front door. I just took the poop in and they gave me medicine. As far as the pee, it could be anything, urinary tract problems, behavioral, etc. Do they like their new food? If they don't, maybe they are stressed and showing it by peeing on the floor? Is the pee that is in the litter box big, or just small dribbles? When my cat had a urinary tract infection, he just dribbled, and started peeing on the floor. I would suggest taking them in just to be safe, the vet can test their urine and stool and let you know. Was there anything else you changed, even something as simple as a new cleaning product or you moved some furniture around? Cats can be very persnickity, and the slightest thing can set them off, and not using the litterbox is usually the first indictation.

In addition to what fosterkitty said, I would add that sometimes if one cat is sick, and therefore pees or poops outside of the box...then another cat will see the mess and leave their deposit next to it, as a statement. In a case like that cat #1 is sick and cat #2 is just responding. Hope that makes sense. Since you're finding both types of waste I would guess it could be a case like that. It seems unlikely to me that one cat is doing both...but it's possible.

Time to see a vet and get some tests run...

Have you recently changed the brand of litter? Sometimes they will go outside of the box if they don't like the type of litter you use.