Why do these tips appear to be pointing slightly downwards, they look like hooks?

N-tox does cause clawing, but i don't see dark or glossy leaves... If you do something starting today, i would drop N 10-20% while maintaining other levesl of typical fertilizer that you add according to the schedule. It looks minor and slow-moving, so it should not require a major change... just a little off on what is provided over time. You also might want to see how it progresses... again, a benefit of a mostly healthy plant and a slow-moving problem. Take a moment to look at color of your leaves with normal room lighting and not a grow light... they may be darker than they appear under a grow light and that would help be more confident about the guess.

too much N, try to give less biogrow, use the sheet but divide it by 1/2 or even 1/4, next watering without nutrients