Certified GKH Gardening Expert
It should not be doing this. There are several things that could be causing this, from pests to fungus to too little water. Given that this has been a dry year for most areas and this is a relatively new planting, my first suspicion would be that this is a water issue. While these are very hardy plants, all plants need water to help them get established because their root system is not developed enough to find water for itself. I would recommend giving the plant supplemental water for a few weeks and that should correct the issue.