Silver Birch problem identification help

[EdithGrantham]

I have a silver birch (betula moonbeam) which I planted out last year. It has had lovely new leaves on this year but some of them have started to yellow and curl and have brown marks on the underside near the stem (I've attached photos) Other leaves seem healthy enough. Any ideas on what this could be and how to fix it would be much appreciated.

I'm absolutely no expert but I can't help thinking that's drought damage. We've had some very very dry weather - depending on where you are obviously.
Presumably no signs of any pests? How dry has it been with you?

Up until this week it's rained every day so I actually wondered if it was over-watered (I noticed the problem last weekend) but when I googled it came up with so many different ideas I thought photo ID might be better!

No other signs of pests that I can see.