My first thoughts are a
nutrient deficiency, although I wouldn't rule out pests either. But here is a link that lists both the
Roles of Elements in Plant Growth, and symptoms of
Nutrient Deficiencies. You can even download it in pdf and print it out, although the full document is 25 pages.
HS787/CV265: Fertilizer Management for Greenhouse Vegetables - Florida Greenhouse Vegetable Production Handbook, Vol 3
I would also email the pictures in this tread, as well as the other thread to general hydroponics, and/or the nutrient manufacture of the
nutrients you are using, just to see what they think also.
General Hydroponics tech support;
tech@genhydro.com