Are you sure you actually spun up Luna sub agents? Sol up until recently could only spin up Sol and Terra agents and would even name them "Luna" despite not being so, you can check in your usage whether it was Luna or not. I believe now it's fixed though.
https://www.reddit.com/r/codex/comments/1vj3hhn/wait_so_sol_...
https://www.reddit.com/r/codex/comments/1vp0rig/sol_can_fina...