Summoned Elder Guardian are despawning

I have summoned 3 Elder Guardians, but somehow there are naturally despawning. Do I need to name them to make them not despawn? I thought this was not necessary for Elder Guardians since they do not naturally despawn.
This is what I used to summon them
execute positioned as @e[tag=RegOceanMonument] run summon minecraft:elder_guardian ~16 ~4 ~11
execute positioned as @e[tag=RegOceanMonument] run summon minecraft:elder_guardian ~-16 ~4 ~11```