First Grow, CBD

The CBD Critical Mass is doing great... shes packing a noticeable amount of bud on every day. The smell is beautiful. Such a sweet citrusy smell, with a hint of spice. It's strong now; I know the carbon filter works! The other two seem to be doing great. I switched to 12/12 3 days ago and they're both starting to flower now. The Peyote Cookies got a little too tall, so i tied the main tops down to bring the height down, exposing the smaller bud sites underneath the canopy leaves directly to the light. Might do this to the Blue Shark too, it seems to be stretching a little. The Blue Shark is the bushiest of the lot. I have great faith in this plant, it has remained strong through thick and thin. The only thing is that the top leaves are very light green as you can see, maybe almost yellowing. I gave them a feed and moved the light up to about 21 inches away since they'd grown so much closer... I'm wondering if they are being bleached, or they're being deprived of a particular nutrient? I fed a full dose of Fish Mix and Bio Grow after the last flush to make sure that they have enough N, also a bit of Bloom and Top Max as they'd just been switched to 12/12. Seemed to help a little, but i'm hoping that with the light being further away, it will remedy this issue... Or I'm gonna be stumped.