Peeing outside of the litter box (vet checked, healthy)

We have a (almost) 2 year old male cat, named Kirk, who has been peeing outside of his litter boxes. We also have two other cats (2 years old, male & female). Everyone is spayed/neutered, not declawed. 

A couple months ago Kirk got locked accidentally in the babies room and peed in the crib, clothes, etc. I didn't think anything of it because he was stuck in there, doesn't meow to get out and had no where else to do his business. But for a few days he has been peeing outside of his litter box. I know it's him because I've caught him doing it. We had a newspaper on the ground that he peed on, the babies blanket, my jacket, clothing. They have 3 litter boxes that are all clean, we haven't changed litter or brand(we use silica crystals). Nothing has changed, aside from having a baby 6 months ago. We took him to the vet but there wasn't anything wrong. I don't know what to do about it. We can't have him peeing on the floor, especially with our baby just starting to get mobile. Kirk has never had any litter box problems before, or any problems at all. He's a good cat and is otherwise acting completely normal. 

This sounds like anxious behavior to me. Being locked in a room can really stress cats out and trigger other behaviors such as what you're seeing now with peeing everywhere but the litter box.

You could try some calming spray but I'm also wondering how many litter boxes you have? Part of this anxious behavior could be him trying to find his own place in a household with 2 other cats and a new tiny human.

Sorry I just saw you wrote 3 litter boxes and I can't edit my post on mobile so I'm curious if maybe he has some favorite places he likes to be that have been changed recently as well? I'm sorry for double posting I know that's not good on forums.

He still pees in the litter box, as well as outside of it. I'll try some calming spray, is there a preferred type/brand? 

I have 3 litter boxes. 1 XXL one that they all pee in, 1 plain regular one that they all poop in and 1 covered on that they don't use too much. All of the litter boxes are in the laundry room, which is the only place we can put them. We have a small house (no basement) so the only space for the boxes is the laundry room, which is a good sized space. 

I personally like Nature's Miracle but there's also one that Jackson Galaxy recommends called Spirit Essences with an herbal remedy for almost any issue. Also Nature's Miracle has some good urine clean up spray that neutralizes the odor to prevent future peeing (hopefully).

I'll pick up some cleaner today. We moved his cat tree, and he hasn't used it much since we moved it. We moved it to the other side of the living room. That was maybe 3 weeks ago.