I'm at a little bit of a loss as to what to do right now.

Lexi has started peeing everywhere BUT her litter box in the past few months. It's gotten really bad lately. I find it EVERYWHERE! She pees on the rug in front of our door, in my room (on clothes, on the floor), on my sisters SHOES...it's awful. Every time I find it I clean the area really well so it's not like she's smelling it and just peeing there because she smells the pee. We've got 4 litter boxes that get cleaned daily for 3 cats, so it's not like it's a matter of her being turned off by that.

She just turned 9 last week, which is one of the bigger reasons I'm starting to wonder if maybe it's something health related. Up until a few months ago, she was perfect. Even when we brought a 3rd cat into the house (and also when we brought our Basset puppy home) she didn't do anything of the sort.

She goes to the vet regularly and nothing strange has ever popped up, though she her last visit was about 4-5 months ago (she got a full senior check up and everything came back good then).

Right now, the room that houses all of the litter boxes is blocked off by a baby gate. It's to keep Babs out, but the cats can and do jump over it without too much difficulty. I know that she hates the baby gate in front of the door to my bedroom though, so I'm wondering if perhaps she's avoiding the gate? I know she can get over it fine, though.

*sigh* It's really disgusting, and I need to find a solution before my dad loses his mind completely.

Any thoughts as to what could be causing this? Any tips on how to get her to stop peeing everywhere and get back to using the litter box regularly?