These gsc “autos” (only flowering now at 15+ weeks after I switched lights to 12/12 :/) are suffering seemingly the same thing (both get the same treatment). They’re kept at 24C with plenty of air circulation and have 2x 75W CFL’s and a 100W LED board. Water them whenever they’re dry about an inch down usually 3ish days feeding with Canna Terra flores on their schedule and potted in Canna Terra pro medium. I use a dropper kit to test pH and seems to be on the mark out of the tap once I add the flores, about 6.3.
They have been a problem since the start and it’s been so long I just don’t want them to die now they’re so close . The yellow leaves are advancing up the plant quickly starting with the oldest leaves. Leaves go yellow/chlorotic before the veins while they remain green then eventually dark/purple and the serrated edges seem to also curl upwards and go purple?