I might have to agree to disagree on that. Coco is a good buffer because it has a high cation exchange capacity - unlike rockwool or perlite or hydroton or other types of reduced media water culture - so binds cations that would otherwise build up in solution and start the process of reverse osmosis, where the concentration of nutrient in solution exceeds that of inside the plant, and starts to draw water from the roots in the opposite direction to which it normally passes to balance the equation on both sides.
All the issues I've had so far growing in coco under LEDs have been related to underfeeding, rather than over-feeding. Either the LED light, being a much fuller (complete) spectrum than HIDs, is driving photosynthesis more efficiently, or I've simply been underestimating how bright they are for their power consumption.
Your plants don't look like they need less nutrient to me, but that's just my opinion, and I have quite a few years experience growing in coco.
Now, you can try underfeeding them - and if it works, fair play - but you could also try increasing the concentration or, as you have suggested, cut down on the number of waterings each day to allow nutrient concentrations at the root zone to build more due to evaporation and reduced flushing. By slowly increasing the concentration, you'll soon know if that's what the plants need and the worse that can happen is you start to burn a tip or two - in which case you simply flush and start again.
I'm not writing this to be argumentative - it's what I honestly believe.