Double Grounding Sub-Panel
The inspector should have red-flagged 2 or more circuits to the same outbuilding.  That's not allowed.
There should be a subpanel alright, but it needs to be on the garage, and then the mandatory grounding rods are a straightforward matter.
The grounding rods are no substitute for a ground wire; they do different jobs.
Since Code does not allow multiple circuits to an outbuilding, it is difficult to advise how to attach them to a local grounding electrode system.