i didnt think it was nute burn because when ive had that before it cam on straight away and it was on the tips. this has taken over 2 weeks. i was thinking mag def from this thing i read about growing in coco. ill paste it below
Magnesium deficiencies normally start in the lower leaves. The veins remain green while the rest of leaf turns yellow and shows chlorosis. The leaves eventually curl up and die. The edges of affected leaves feel dry and crispy. As the deficiency continues it moves from lower leaves to the middle and upper half. Eventually the growing shoots change from pale green to white color. The stems and petioles may take on a purple color.