I've been having this issue w Coco under LEDs for a while and after chaising my tail I came to the conclusion that my high VPD was causing my plants to uptake too much calcium during transpiration, causing Magnesium and Potassium deficiencies.
The first sign was plants that were perfectly happy vegging under my T5s, would droop and curl badly just hrs after they were put under the LEDs. Then I would get the yellow spotting on the upper leaves, leading to full on interveinal chlorosis. (Mag Deficiency) Lower leaves would yellow and scorch from the edges inward, stems and petioles would turn purple and growth would slow to a crawl.(Potassium Deficiency) I was also getting tip burn at insanely low EC levels, but the plants would always show those same symptoms yours have.
I stopped my calmag supplementation for 2 weeks, raised my temps and humidity to about 80F, 70%Rh, and everything is finally pulling around and giving me lush green growth again. After doing tons of reading and research and pulling my hair out for months, this was the solution for me. It was all because my low humidity. Was never a problem under HPS or T5s, but proper LEDs made them freak out until I got VPD in check.
This might not be the case for you, but figured I'd share what I've found since I see the same symptoms with your young plants