Could this be mosaic virus by chance? It's effecting new growth and one plant only...all plants are in identical media, receiving the same amount of water, same nutrients,lights etc.... i'm totally stumped, has anyone seen this?....
Looks like that leaf formed that way from the beginning. Not all leaves come out perfect all the time. I wouldnt worry to much. I have a gg#4 that half the leaf comes out lime green on one side and darker green like normal on the other side of the same leaf. Entire plant is like that, but she is budding great. Have clones from her and their the same. Just make sure things arent appearing to go like that on more leaves. Mine is a genetic defect.