I'd do the carbs thing for now, not the Cardio.
The fact is, if the Cardio is working, why change it as well? If it's not and the Carbs thing doesn't change anything, then go for the Cardio change.
If you change two things, one aspect may already work well, but you might make it work less well if it's changed, then it will work against the other necessary change to hinder progress, if that makes sense.
Isolate one thing, make change, assess what happens, then after 2-3 weeks go from there