It looks just a bit early for natural die-off to be happening.Yellowing leaves means the end is near. Watch for more leaves to yellow.
I think you're right. discoloration not uniform.It looks just a bit early for natural die-off to be happening.
Perhaps his soil is depleted of N?
Just a thought.
I'm using fox Farms ocean Forrest and I have cut back on ff Grow Big which could explain yellowing, should go back to using FF Grow Big for the time being??Assuming the media is Super soil (just a guess) I would add a mild worm casting tea to see if it helped.
But that's me.