What is wrong? In the tent its 17 °C. The water is fresh, no fungi at the roots or in the water.
Light time is 18 hours on and 8 hours off. I use Hesi Hydro Grow.
The EC is now 1.18, thats after the water refreshing, before it was at 1.6 EC.
I found the problem: your day has 26 hours (18+8h) 😂
But on a serious note, I'd agreed with the other people here. It looks like a nutrition burn. Maybe your pH / ec meter isn't exact / broken or the fertilizer concentration is too strong. I'd try to flush everything and just use plain or even destilled water (but I don't know to much about hydroponic growing)
Anyways, good luck with your grow, you got this 👍
bad genetics heat stress wrong ph nutrient defiencecy or all 3 orr could be ur ppm is to high so it cant absorb i dont know looks weird....is ur meter calibrated right?