Axolotls keep disappearring after spawned

I have captured three axolotls in a realm I share with a couple friends. I built an enclosure for them and made sure that it was lighted so no mobs could spawn, and no openings that my pets could escape from. I logged onto the realm yesterday, and all of my axolotls were gone. None of my friends had anything to do with it, and there is really no way they could've escaped, so the only possibility was that they despawned. When I asked Reddit about the issue, I was told that animals can despawn if they aren't nametagged, so I made a point to nametag the next ones I caught. Today I logged on, and one of them was gone again. I don't know what could've happened, other than a bug caused them to despawn. Pleass fix this issue, because I love the axolotls and it sucks that my pets keep despawning. I play on Nintendo Switch, also, if that makes a difference.