Yellowing tups....

This appears to be a nutrient toxicity. Since it’s starting at the top and I see your leafs are very dark green makes me think you have been over feeding. I suggest you flush your media out with pH adjusted water at the rate of 1-2 gallons per gallon of soil. This will remove any build off of nutrients in the soil that have accumulated over time. Remember when feeding you need to have about 20% run off out the bottom to wash away the old salts so they do not build up. I hope this helps.

Overfeeding mate. Lower your feed. You dont need a total flush. Just add something that will lower the ph around de roots that will increase nute uptake. PH if not organic needs to be In the area of 6.7 this will allow for peaks and lows. Its the optimal soil ph 5.8 for coco/DWC.

Not lights, but generally way over fed and suffering from a zinc deficiency. A dose or three of soluble trace elements/minerals mix (available from any decent gardening store) should help with the yellowing. But you are feeding them too often or too much........or both....... generally.

It's not light, it's nutrients. Looking over your diary it appears you've used lots of different brands/products over the course of this grow. It's possible you've created a bit of nitrogen lockout. In flower you don't need as much nitrogen but they still need a little. I'd give plain water for a couple feedings then slowly reintroduce nutes following the manufacturer recommendations.