Hi, that is ridiculous. Not sure what state you are in but we are in Victoria and we rented out our home for 18 months and while tenants did mow, they did not weed and pulled out numerous plants they said had died. Basically all they did was mow and our RE told us the upkeep of gardens Is very unclear in tenancy act. (but our re was hopeless as they let the tenants wreck the place) It sounds like you are doing all the right things and RE is being over zealous!!!!