Probably the hydroton raising the ph out of range, I’ve had new hydroton that I just did a quick rinse raise the ph and kill a young teen before I realized what was going on. As for the feeding schedule/recipe you posted I see no problem with that, I use a similar recipe with no problem. But I do believe you need to dilute that down until you see the new growth straighten out and lighten up in color a bit. Nutrient strength for LEDs is less than what most folks are use to with other light sources. I start my ph at 5.5 and let it swing to 6.5 so I hit all the absorption range, 5.8 to 6.3 is fine though. With your ph swinging so high I would say your hydroton needs flushing with a lower ph, at least 5.5, if you have your overflow set where you can submerge your hydroton without any floating I would just let the pump run recirculating the water and ck ph periodically and adjust as necessary until you get it to stay at a suitable range. It doesn’t matter what the plants look like now when you hit the sweet spot with everything, the plants will recover rapidly.