According to wowhead:

• the Cervid Soul drops from Prototype Pantheon (Sepulcher of the First Ones).
  https://www.wowhead.com/item=190337/cervid-soul

• the Gromit Soul has a chance to drop from Shrouded Cypher Cache in Zereth Mortis.
  https://www.wowhead.com/item=189983/gromit-soul

• the Ray Soul can drop from Enlightened Broker Supplies, the paragon reward from The Enlightened.
  https://www.wowhead.com/item=189973/ray-soul

• the Silithid Soul drops from The Jailer (Sepulcher of the First Ones).
  https://www.wowhead.com/item=189982/silithid-soul

• the Snail Soul drops from High Value Cache inside Sepulcher of the First Ones.
  https://www.wowhead.com/item=189991/snail-soul

Thank you for summarizing all of those, will update asap.