yellowing leaf problem.

What should I do if my 3 week flowering ladies have yellowing leafs. I believe it is N def.

Up until a about a week ago I was giving them General Organics BioThrive Grow. then I started the pure blend pro bloom formula. I think the ph is between 6 and 7. Should I add any cal-mag.
or is the PH even correct?

I know that the yellowing leafs wont turn back to green. but I just wanna stop the other leafs from turning yellow.

medium-coco with perlite
Indoor - 180W LED Grow Light/3W leds
Strain - bagseed
Temps - 70 or so
12/12 for 3 weeks.
here's 2 pix.
This image has been resized. Click this bar to view the full image. The original image is sized 804x669 and weights 124KB.
This image has been resized. Click this bar to view the full image. The original image is sized 824x618 and weights 124KB.

I think the problem might be that I haven't been giving them any of the calcium + magnesium I have. plus I just notest that both the veg and bloom ferts I have don't have much Ca or Mg in them.

So the next watering IM gunna give them some. hopen it will help.

It doesnt look like Mg def to me. Mg doesnt really cause uniformly chlorotic leaves. Looks more like Nitrogen. The fact that is is affect older fan leaves also points toward N.

Ca def is easy to diagnosis by the yellow/brown necrotic spotting on leaves. Leaf tips may be curled and/or burnt as well.

"Taco" leaves, inter veinal chlorosis, red petioles are common Mg def symptoms.

What is your water source? If you are using RO, distilled or "soft" tap, and not supplementing Ca & Mg, there is a good chance you'll run into issues esp Ca in flowering.

What are the NPK values for the fertilizer you are using?

well I did end up giving some of the cal+mag to the plants because I haven't been given em any. The water, I fill a half gallon jug with tap water and the rest with fresh brita filtered water then add my nuts then check to make sure the ph is good then water plants.