Well theres a couple things going on in those shots:
1) The veins are green but the leaf centers are fading to yellow, so thats a magnesium deficiency.
2) The tips of the leaves are starting to yellow, coupled with spotting through the leaves, looking a bit like the start of a calcium deficiency. This is probably more due to magnesium being low / locked out which makes calcium less available to the plant.
I'd start with a foliar spay of epsom salts at a 1 tablespoon per gallon. Hit the plant once a week for the next few weeks and it should green right up. You can water with magnesium or calmag like products as well, but the results will be MUCH slower than foliar sprays.
