nodes look tight at the top.. possibly slightyl too much light. looks like 3 sets of leaves are bunched up near each other.. it should be a bit tighter around new growth but then steadily space out a bit.. otherwise it is indicative to too much light... which would also cause top leaves to be paler than the rest too. coco isn't magical.. it's just soilless substrate. You need a full diet. there are apps that can calculate this tuff from your gauranteed analysis labels and tabulate it for you. for vege: 120-130 N 40-60 P 180-200 K Ca 100+ Mg 75ish S 100+ this would be a light concentration but well-balanced and will scale up up well if necessary. Ratio is as important as overall concentration so that you don't inhibit anything. This isn't "my" formula. It is one derived from empirical studies and re-used by multipl professional agricultural fertilizer producers not branded with teh marijuana leaf, and a couple that are. it's not some esoteric formula created in some shut-ins basement.

Hard to say without a diary for info.....could be lack of nutrients, could be PH is off causing a lockout of certain nutrients, could be lack of light to drive nutrients uptake.

worm castings