I agree, your pH is too low for a coco grow. 5.8-6.2 is good for coco. also, your P and K is too high. your N is too low.

Before adjusting nutes, adjust pH first. see if the problem corrects itself.
the purple stems and yellow leaves show signs of N deficiency, but your leaves are also showing signs of nute burn.

pH first, then nute adjustment.
GanjaRobPDX Reviewed by GanjaRobPDX on . Something wrong but I don't know what Could any please give me some advice please, I am currently growing 10 plants under two 600w metal halides, the are in 15 litre pots with canna coco I am feeding ph 5.5 Canna coco a&b 10ml per 10 litre of water Rhizotonic 20ml per 10 litre of water. Rating: 5