I have 4 cats. A while ago I noticed that one of them peed on the floor. Then I found pee on the sofa and on my new t-shirt! It wasn't easy to track down who the culprit was!! One day, while 3 cats, Maya Inka & Zazou, were playing in the garden, I found a new pee-puddle on the floor. This time I knew it had to be our little Snoopy! I tried to pick as much pee as possible with a syringe, put it in a glass and brought it to our vet.
She found out that Snoopy had a bladder infection and some chrystals too.
After 2 rounds of anti-biotics, it is much better!! Once in a while Snoopy still pees on the floor, but it is always when she is in heat. I hope that this problem will be solved too after tomorrow (she is getting spayed!)

Good luck finding out the spraying cat! And, welcome to Pet Talk!!