Leafs with copper patches on Beech hedge?

I've planted a new Beech hedge this year, and its currently about 4' high. 4 Days ago I sprayed with Bayer to remove Woolly Beech Aphids.

I've noticed that some of the leafs on the hedge have started to turn copper/rusty. Can anyone identify what's causing this?

Regards

 

Beech doesn't do well in cold spots. Are u prone to a lot of frost? It also may be that the soil is waterlogged or clay? Any of these present?

 

Hi Gwen - no, neither of those...