From your description I believe it could be one of two things

Either there is too much nitrogen in your mix (the plant needs much less N during the flowering stage) OR your roots aren't getting enough oxygen

I hope this helps, pics would be very helpful

And I really don't think that the yellowing of a plants leaves that early into flower is a genetic trait, you really only see that normally happening on healthy plants during the last two weeks of flower
SunnyD Reviewed by SunnyD on . leaf curling down I have some white widow two weeks in under 600 hps, feedin them on bio-bizz my temp is 75-80 and Rh is 30-40 the leafs are startin to curl under and a few yellow spots appeared on a few of the plants i dont understand why. any suggestions? i had a few probs with temp and Rh for first week or so but have sorted that out now my temp was 85 and Rh was about 20 could that have caused them some heat stress? Sorry theres no photo ill try get one on. Rating: 5