Hi Hedge has it been very hot where you live - could the plants be thirsty?
The alternative id the horrible thought you have blight...

thanks for that. we dont think its blight when we checked with photos. We think it may have something to do with the manure we dug in at the end of last year. Has anyone heard of problems with manure.

Where did your manure come from?

Horse manure from local stable

did you dig it in the previous autumn or just put in the trench? If the later it is possible it is a bit strong but I'd get the potatoes watered.

It was dug in while digging the trenches. we have heard that t could be too much amonia, It has rained quite a lot in our area so we are hoping that might solve the problem. thanks or your ideas.

Himself puts compost in the trenches but wouldn't want to use horse manure - hopefully all the rain will help.