Who gets picked on the most? I have a similar problem. The other cats pick on Ivy alot, to the point that she sometimes can't use the litter box. They chase her out. So she is the only cat allowed in my computer room(except Sophia for now too). She has her own toys, scratching post, treats and litterbox. She spends a few hours a day in this room and it greatly reduces the tensions in the house. That reduces the peeing.

Onyx is a behavioral inappropriate pee-er. My vet says Onyx would prefer a home with a few less cats. Since that's not happening, we have done a few other things for him. Onyx likes to pee on hard, flat surfaces. Since peeing on the kitchen counters is not acceptable, I have an almost empty litterbox for him. It's has to be cleaned more often, but I can do that. I often leave the bathroom door open for him. The tub and sink are easier to clean than the counter!

I have feliway diffusers throughout the house. One in every room. I think they do help. I put rescue remedy in their water. Not so sure it does anything, but it can't hurt. I find it's more effective with the dogs. If it does nothing for your pets, take some yourself! Might take the edge off your stress!

I use a SSScat bottle on the cupboards at night. It is motion activated, beeps and shoots out compressed air when something sets it off. It's very effective.

Good luck!