Posted: 04/07/2012 at 06:27
Can you post a photo of the problem?
Here are some photos of magnesium deficiency in potatoes. Scroll down to photos 161 and 162 and see if you recognise the symptoms.
Bah! The link system still doesn't work here. Cut and paste this link into your browser:
EDIT. Oooh! The link system is working now. As is the edit system. Happy days!