My Kittens Are pooping Everywhere but their Box

Genie's kittens are almost 6 weeks old(this fri) and they haven't used their box yet. I have litter boxes with various litters all over the house(they have free access because they started roaming and I figured let them). However they have adjusted to eating wet and dry food but for the life of me they will not use their litter box. WHY? My vet says it might be worms but what has that got to do with it? THeir stools are solid and I am working them today but still, isn't it instinctual? I am doing nuts cleaning up poop and pee everywhere from little kittens!

I confine my kittens for the first 3 months in one area until I KNOW they are using the pan every time. By letting your kittens have free access you are confusing them.

You need to have shallow pans (no more then 2 inches high) for awhile. Young kittens may not be able to climb in and out of a small litter pan that is 3 or 4 inches in height.

It takes them a few weeks to be reliable and use the pans consistently. So confine them to one room with one or two smaller litter pans (use a tinfoil cake pan) and only let them out for short supervised periods of time during the day/night.

I've never had any issues potty training a kitten, what I do is put them into a very small room with a litter box + food, etc.

Like most animals, they do not like to soil their play/sleeping area and will eventually use the litter box if kept in a tight space. Once they get the hang of it for at least 2 weeks or more ( be sure they are all using ) you can let them roam free because they always go back afterwards!