Previous worlds in peaceful mode no longer naturally spawn mobs after latest updates

I am new to this reporting bugs things so forgive me for getting any of my information wrong. I had a world that worked perfectly fine in the update before 1.14.3. I left the world in peaceful mode and went to bed for the night. I didn't go on for a few days and when I decided to go back into that world there had been the 1.14.3 update. I went into the world as usual and changed the difficulty to Normal. It was night time and typically there are plenty of mobs where I built my house. I went looking around so I could get some experience and there were no mobs. I managed to find 2 spiders in a cave, but those were the only two hostile mobs I could find. Passive mobs still exist as normal and I cannot keep track of their spawn rate. I went exploring the next night and some phantoms were able to spawn and attack me as normal. Still there were no other hostile mobs. I went into the nether and saw some pigmen. It seems like only mobs in the overworld are messed up. I'm not sure if this is a glitch or an issue on my part or something? I backed up the world when it asked if I wanted to.