Thank you! Can you recommend a plugin that could do this specifically?

WhiteThunder

Mass deleting planners will break many legitimate held entities, causing items to no longer work. Any deletion of planners should be done selectively (by plugin logic) to verify that they are no longer able to be used by players (i.e., not in containers).

Laurzapann

Thank you! Can you recommend a plugin that could do this specifically?

Nivex has one in his Discord community called ItemLeak. Reach out to him for an invite.