Looks to me as if mostly just the flowers are brown. That could be from transplant shock or as Jean suggested, a late frost could do it, too.
There are still some healthy looking leaves which is encouraging. I'd cut off all the brown flower heads and see how it does. Maybe shading it from the hot sun for a while would help it recover from whatever happened, too. IF you have a piece of shade cloth, that would be perfect, just make a little tent over it. An old sheet would work, too.
