New Cherry Laurel Hedge - Help Please

Hi, I'll appreciate any advice on how to get my hedge more healthy looking. It was planted around 6 weeks ago, stems were trimmed to around 40cm tall when planted.

Many of the laurels have developed curled up and brown edged leaves as you can see in the photos. I've done some research but not found any conclusive treatment / remedy that I can apply.

When planted, I used root grow and mixed bone meal in with the top soil top soil. The plants came in 2 litre pots. I have watered regularly to keep the ground moist. I also sprayed them with bug spray a couple of weeks ago to see if it would help but no improvement seen. I haven't 'fed' them yet as I hear it is best to let them seek out nutrients by developing strong roots - I have some miracle grow I could use if advised.

Thanks in advance.
O.