Not sure if intended, but Rainbow Jelly don't reappear after they are killed in some area.
Normal Jellyfishes do respawn.
Steps to Reproduce
1. Kill Rainbow Jellyfishes in certain area 2. Come again to same area in 10 days - no Rainbow Jellyfishes are there, they did not respawn
This issue has been closed either because it is not a bug or does not belong in the bug tracker.