Yellowing leaves week 6

The leaves near the bottom of my 3 plants all simultaneously started yellowing 2 days ago. Here are some pics of the leaves and plant. Other info: jack horror auto, 6 weeks old, fox farm nutes, dropped grow big last week, lifting to determine watering, ummm temps kept between 80 - 85, and rh about 40.
If anyone has any advice it would be greatly appreciated. Peace

This is a normal occurrance. Your beauties are simply using up what little N is left for them to take up. I usually Give mine a lil worm castings to provide for a slow release N, and a lil P and K, as well, about halfway thru flowering, so that my fan leaves all stay a healthy, green color for the duration of flowering. But, at 6 weeks, I would say that mabye just a lil bit of N, and I cant stress how lil, but a tiny feeding with an N-rich nute will solve this "problem"...
Absolutely no need of worry, either way... U almost don't wanna put anything on em at all, as close to maturation as you are... Normlly, I'd be flushing around my 6th or 7th week, for the last 2 or 3 weeks of flowering growth...

I thought I had read it was normal. Thank you for the reply. I'll give the ladies a little n and see if it doesn't help.