Not a lot of people talk about it, but I keep noting that more and more of us are turning the intensity down at about this point. The leaves are showing fatigue, whatever the reason, and we tend to blame it on nutrients, etc. But it's a balance with weak links. I think high intensity is one of those links. Ease off the lighting and the plants usually look better. They quit fading and the new growth looks better. And a key signal is looking at the growth lower in the canopy. I used to marvel at how frosty some of that stuff gets!
All plump and delicate with insane frost?
That deep into the canopy?
Drop the intensity 20% or so until harvest, and I bet they love it.
If you can just move the plants away though, you'll have a deeper effective canopy. Better than having less light overall. That's all I do - just drop the plant lower.