Slimes not spawning

I purchased a map called castle architect in the Minecraft store by pathway studios and I noticed after making this map my realm that slimes don’t spawn in swamp biome’s this is a survival map where achievements can be earned. I traveled to three different swamps within this map one of which was a small swamp two were quite large. Stayed two Minecraft nights in each swamp stayed three Minecraft nights in one large swamp, saw and fought all the other mobs but not once did I see even a small slime. I’m assuming that because it’s a store bought map that slimes spawning in swamps isn’t affected.