Nitrogen Toxicity??

If your using Coir and not watering with 30%+ adequate runoff your leaving nutrient salts behind causing lockout and high EC at the roots. Water more often after the flush with your normal nutrients. If you let it dry too much the salts will bind to the coir and your EC/PPM output will steadily increase over time and see problems like this.

Are you also noticing purple veins and/or purple streaking? Calcium needed and the purple is usually from magnesium deficiency. I had a very similar issue last week and a dose of calmag sorted it out in a day or so At that age I would try 50-75% of stated dose of your base nutes. You can always add more so work up as she gets bigger and watch the tips for signs of burn.

Make sure your using Cal-Mag Plus at 5ml per gal. Use %75 nutrient strength and every third watering use straight RO.

Nitrogen Toxicity It causes dark green leaves and curled tips, [the claw] From what I can see from the pic you have Nitrogen Toxicity, Overwater, and Cal-mag.

in first photo looks like leaf was heavy dark, but now returns, but hard to see, lightning not best. second is more calcium or ph issue, could be calcium lockout from N excess, but your leaves dont look like that heavy dark, more watering, ph and calcium, than anything else.

Looks like necrosis of magnesium and calcium deficiency to me