Slimes are either not spawning or spawning VERY rarely.

What I expected to happen was...:
Since I don't have a swamp near me I went about trying to find a slime chunk the old-fashioned way. I dug down to Y level 0 and made a 3x3 wide tunnel and when I saw a slime spawn I marked the chunk it was in and cleared the area end to end with a 3 high spawning spaces, lots of light, and then proceeded to clear 2 more layers. One above and one below the one at Y 0. After that, I went and lit up all of the caves and areas nearby.

What actually happened was...:
After all that I have only had ONE slime spawn which was the initial one. I thought since the generation update that maybe the required Y level was lower in the world so I dug down to Y -45 and made another spawning platform area. Still, nothing spawned. I checked in spectator mode around me and there are no other mobs around. While facing that chunk on the f3 screen is shows me that only three entities are loaded so there isn't some pocket of mobs in a cave causing there to be no spawns. very confused about why they aren't spawning. Have the spawning rules changed? I didn't see that in the changelog if it did.