possible nitrogen deficiency

also

possible IRON deficiency.....i'm looking through my book and the closest matching picture is for Iron deficiency

symptoms -- younger leaves and growing shoots turn pale green and progress to yellow between the veins starting at the petiole but the veins remain green. more and more leaves turn yellow and develop interveinal chords

to treat - lower ph to 6.5. avoid nutes that contain excessive amounts of manganese, zinc and copper. high levels of phosophorus compete w/iron uptake. improve the draining....excessive wet soil hold little oxygen preventing iron uptake. damaged or rotten roots also prevent iron uptake. apply chelated iron in liquid form to root zone. must be thorogouly mixed with growing medium. don't expose the nute solution to light.....leaves should green up in 4days approx.

hope this helps