It's called transplant shock and it can happen to just about anything planted at this time of year and just gets worse as the season progresses. Given proper care, the plant will grow out of it. Make sure it gets adequate water and it wouldn't hurt to provide a bit of afternoon shade as well.

Did you absolutely soak it after planting? If not do it asap. Imagine it’s a vase of cut flowers for the first few days while the roots are settling in and starting their work.

you dont mention size.. but if you can rig up some shade for a week.. it might help the stress level ...

ken