Zinc deficiency?

I think you may be suffering from a little heat stress. The plant itself looks really health by your diary. The only issue I can see is your day temps. About 5 degrees too high. Pretty sure zinc deficiency shows up as red tips on leaves. I can see the leaves just below the top leaves have a raised serration which always points to heat stress. Your top leaves are probably taking the brunt of it and dry up quicker than the rest, making them fold over on themselves. Raise your light a little or decrease the intensity to lower the temps in the grow space. I hope this helps, good luck and happy growing