Hey Mate,
First thought was too much, or too close to the lights.
But then recognized pH 7 π€
Quite high for coco. Just for your info, pH calculation is based on log10... so pH7 is ten times more alkaline than pH6. That's a big range. So, I would say lights or pH...
Hope this helps a bit, good luck and happy trails for the rest of the way π€
Servus
OimRausch