Nice picture showing the area under the canopy. Looks like a fair amount of effort went into doing it.Edit: the nutrient maker i am using states at this stage of flowering to have ec 2.1 going in and mine is 0.8, i reckon 2.1 going in now would mess with it in someway.
It seems like the cause of the problem has been found. There are not enough nutrients to supply what the plant needs at this stage. One dose of nutrients a day and the nutrients set lower than where they should be is causing the problem.
I don't grow in any sort of hydroponic set-up but I am pretty sure that all you have to do is start giving the nutrient solution twice a day and then gradually bump it up a little bit every couple of days. Watch for bad reactions. The way I see it even if all that happens is slowing down the change in the leaves it is a lot better than letting it get worse and worse every day.
Air circulation problems and high humidity come up a lot during the summer in the northern hemisphere. Over the next month or so check the "New Posts" every day and see what problems others run into and the suggestions to fix the issue. It helps to say ahead of problems.This is why i think my area is so bad the plant grows too big for the space there is little air circulation up top as soon as i close the doors humidity can rise 10%+
my next grow in a tent will have more room and air flow it should be better ...