Sick plants?

Ca def late stage, K def beginig... also probably it's a lock due to over fertelization... there're to little for 1.67 EC flush and feed anew with no more then (water 150ppm if not then add CalMag + veg fert 150-200 ppm) 300-350 ppm in sum 👇😅😂

The extra damage on lowest leaves are probably because they are in contact or too close to the medium. maybe too much P // Maybe a bit too much light not enough info. Is that a 2x2 space? 18 hours and 120+40 = 160 watts is probaby 50% too much even if lower efficacy. Take your light(s) cumulative umol/s production and divied by m^2. reference a DLI table with hours of operation if if it's drasticaly above 35-40 DLI, you need to fix the light situation before assessing leaf symptoms.

looks like to much light, not enough airflow because of how compact the plants are and to much feed with buildup and PH issues.