I have the same issue Chromophore. Interestingly enough, only the T5 light girls have the yellowing of leaves. The rooted clones were having the same type issue as well.
I repotted them in....Gasp!...GOOD SOIL! Hahaha...finally stepped up to Happy Frog and bought some FF's "Grow Big" too.
They are looking better today. The point of this is Nitrogen....(at least I think that was the issue) which they got with the new soil and Grow Big. The color is improving from the very light Green already. Do your leaves exhibiting the Yellowing have red main "Veins?" You are way ahead of me in regards to horticulture, and it's just a thought, but maybe it's a Nitrogen issue.
Doesn't seem like they should be dropping leaves due to using up the N already...and the part that clues me into a potential issue there (in my case) is the fact the HPS plants don't have the same problem and the T5 plants are more developed.
Stands to reason the T5 lights have used all the N in the soil, (or something) that the HPS light plants have not expended due to development at this stage.
Beats me...ramblings of a Newbie.