Are they in the ground or in tubs?

I had some clipped box that foxes took a liking too. I trimmed them and this year they have started to fill out again where they had die back. It has taken the last 3 years though.

If they are in pots they could be root bound, need re-potting into a larger pot. They could be dried out and not have room for watering in the top of the pots. If they are in the ground it could be a disease like canker.

Its a possibility it could be box blight..which is a virus...you could try spraying...but if it has taken a good hold....you may have to destroy....and the virus may stay in the ground nearby.

Are they brown or orange? We've had lots of questions about orange box and the concensus of opinion was that it is caused by cold weather. But all the above comments could also be true. See if the leaves are brittle (box blight)or still pliable(cold).

They were in tubs and I decided they might need moving so they are now in a raised bed. The damage was done before I moved them (about 6 weeks ago) and there has not been any improvement.

Thanks for all your suggestions I will check the leaves this weekend and will probably cover up if you think it is cold

I have the same problem and was just going to post it..so thank you for that. Mine are both in tubs and they have gone increasingly orangey/brown in colour. If it is box blight,what can I spray them with?If it is cold, do I need to move them from the front of the house (north facing) to a more sheltered spot?
I'd hate to lose them.....