Why are my leaves curling down?

001 is half right - u have P excess (stop using any P fert for next 2 weeks untill curling will stop) --Mg excess and Ca lock (this is ur main issue) stop giving CalMag, focus only on Ca until tips of new growth will stop clawing ---all else is related to issues above P.S. not that bad, u have time to fix it into healthy plant, gl.

skinny leaves with chlorosis in new growht -- too much p or k is possible. Paling from inside out at top could be low S too.. but you'd see other symptoms to help discern. google image has plenty of 'mariuana leaf symptom charts' to compare. re-assess any changes to fertilization the last 2-3 weeks. Need more evidence than just visible symptoms as they are not discrete. even if you haven't changed how you fertilize, the culmination of 5 weeks and counting all adds up... if something was slightly overfed it can take a long time before you see negative ramifications. may need to change ratio of your feed from the start - next time. you don't have signs of ca or mg deficiencies, so don't over-do it. too much Ca will lock other stuff out. The stuff that commonly delivers it might raise pH too. leaf curl tends to be overfeeding, but i'd be patient here... see how those symptoms progress.. cross reference with any other relevant info that doesn;t fit into a grow quetion. Do less intrusive things like verify pH hasn't drifted out of the happy zone.

Do they droop more when you water? Can you show me what calmag you're using? I don't think it's nutrient related. I think it's root stress related.