Mom is stumped

Hello blogging friends! The Mom that Lives Here here....I need some help and hopefully, somecat or their beans can help.

As you know, there are 3 kitties that live here. Dazey and Jesse are 6 year old, spayed sisters. Conner is 5 years old and nuetered.

We have 3 litterboxes in our basement. 2 covered, 1 not covered.

Recently, one of my darlings has felt the need to poo on the floor in front of the litter box. I have a suspicion of who it is (Jesse) but have no way to 100% verify this fact. If there is just the tiniest sprinkle of litter on the floor, the offender uses it.

Saturday, I bought a brand new uncovered litter box and threw out the old uncovered one. It's the same litter I have used for quite some time. I did, recently, have to get a different kind because the store locally didn't have any. that's all gone now and that is when the problem started (again). They have been back the regular litter about a month now.

The reason I suspect Jesse is because about 4 years ago, she was doing it then. At the time, my sister had an apartment and took her for about 2 weeks. The problem cleared up as soon as she was out of this house. I think it's linked to her dislike of Conner. But as I stated I have no way to verify my suspicions. This has been going on about a month now. Granted, it's not every day that there is a mess on the floor, but probably 5/7 days. I scoop the boxes, I clean the boxes. I put the brand new box down yesterday, scooped the other two and found a smaller box and filled it too. I go in the basement this morning and there is a mess again.

I need some advice/encouragement/ideas etc as to what to do with this problem. It's very frustrating for me. I'm on the hunt for a new vet, as the previous one just didn't seem to care much about my animals, but more about the check for payment. We live in a relatively small town so my options are limited. I could take her to the vet where she was spayed as a kitten but for one, she hates the PTU and 2-it's 20 miles away. You'll say it's a sorry excuse, but with gas prices soaring higher and higher, I head that way once a week and it's on Sundays for church.

I do welcome all input, thoughts, advice etc.

thank you!
Jennifer aka the Mom that Lives Here