Bee nests are not naturally spawning in worlds created in a previous version

Yes, I know they should only appear in the Flower Forests, Sunflower Plains and Plains biomes, but in my world (I updated it from 1.14.4 to 1.15.1) I've been through several of these biomes and I can't find them
I think the problem is in worlds that were already created in previous versions, because in another test world I could find the bees naturally