potato disease - not sure - curling leaves - please help.

Hi there,
I have 3 rows of earlies and the rest maincrop.  I have curling leaves on 2 plants - the plants in question are 2 rows apart at either end.  
Should I dig them up, leave them or spray them with something.  The leaves aren't turning yellow or going brittle, just curling around the new growth.  Any advice would be appreciated.
Thanks
Fiona