coco deficiencies in bottom/medium canopy leaves

looks like you nee dmore nitrogen from the fade. the brown could be related to poorly prepared coco, if oyu got the cheap stuff, or it could just be too low of nutes. feed more, i'd guess... could wait a sec and make sure that's the case if it detiorates quickly with a couple water-only feeds. won't take long in coco for deficiences to get worse, but toxicities still take a while to reverse course. if you've been light on nutes, i'd fertilize more often than you have so far. coco needs fertilizer every feed... rarely a water only dose.