i think its either nitrogen or magnesium. would a dose of veg nutes (2-1-6) or calmag plus (also has nitrogen) be better?
I agree, although I can't tell which from the pics. Because it is spreading up from the lower leaves, it is a mobile element deficiency thus not sulphur. (2-1-6) are not veg nutes. you want something with a higher 'N' content. When fixing a nitrogen deficiency, you can get faster effects by foliar spraying too.
