Can you add a photo? New plants often don't bloom as well as established ones, so premature browning of flowers isn't unusual since they are trying to grow roots and don't have as good water management as older plants. As long as the leaves are still green, you are fine. Plants take some patience and so you should see better performance next season or perhaps the year after that once they are established. If the dried flowerheads are bothering you, trim them off. I often leave mine in the fall to add decoration to the winter garden, but you can remove them whenever you want. If your plant doesn't have a good layer of mulch out beyond the drip line, add that, and maintain evenly moist (not soggy) soil for the remainder of the season.

You might want to add your location and zone to your profile so it posts by your name. My experience as a gardener here in z 4/5 NH is quite different from Luis's in z 7/8 TX, so depending on where you are you may get other suggestions. Here's how:

Go to Your Houzz in the upper right of every page, click Edit Profile, and on the left side click advanced settings. Well down the advanced settings page is a blank labeled Climate Zone for Garden Forums along with a link to find your zone.

If you add info on your state or the nearest large city you will get even better information since zone only relates to average coldest winter temperatures.

Then return to the top of the page and click Done Editing.