We've had our girl kitten about ten days now. She used any of the four trays we have fine for the first week but now pees and poos in either the bath or shower tray.
We have four trays (three cats, the older two are free to go outside but one chooses to be an indoor cat). I make sure the trays are clean.
Any ideas, I know it could be worse and it's relatively easy to clear up. I've been using an antibacterial cleaner but I'm wary of using anything stronger.
She's eleven weeks old and will be free to go outside when she's been spayed.
Obligatory photo attached 