[2019] Jewels keep despawning in item spawners

So I'm making an attacking and defending type gamemode on Creative, and have 4 jewels about 5 tiles away from each other in item spawners. When I start up the game a go near the jewels in the item spawners, they despawn within about 15 seconds of me being able to see them. Does anyone know whats happening and how I can fix it? Thanks!