Leaves are curling downward, help on what's going on and what to do is greatly appreciated

I think you got it right buddy. Normally toxicity causes clawing leaves. Flush with PH water and it'll bounce back fast. Depending Leaving 2 other ideas that are not likely but can cause that. 2- Not likely but also lots of airflow can cause that. If that's the case then it should be only on the part of the plant that's exposed to more airflow not all over. 3- Check your light's timer. If it's malfunctioning it might re-veg the plant. https://www.growweedeasy.com/cannabis-plant-problems/nitrogen-toxicity