i dont' know about yours, but the discoloration on mine has been due to the light being too close and heat damage to the leaves. the plant's height was increasing so fast than every day i would find the plant touching the light, which was pretty warm. happened a lot when the plant was smaller, but once i got the light far enough away they returned to a nice shade of green. now that it's bigger, i'm just trying to find that right height to keep the light at again, and my leaves nice and green. i don't know what your setup's like, but the light could just be too close.