I've had the same issue with some of my veggies. The tomato was corrected easily with some lime and some nitrogen. Have you limed your tomatoes yet this year or fed them?

GGG

There can be several reasons for any veggies/flowers to have very light green leaves:(1)Nitrogen deficiency (2) Too much watering (3) both 1 & 2. (4) Too much shade
If you water your plants exessively, then nitrogen, which is water soluable will go further down, beyond the reach of plants roots. The soil could have been originally poor in nitogen also.
So to remedy, feed your plants. I would just use balanced all purpose fertilizer such as 10-10-10. Or cow manur-compost combo.