Weird mark on leaves

i'd wait and see. could be a few things... if it doesn't spread it's just a growth defect or physical damage one way or another - insect/human/foliar spray contents or anythng else along those lines. keep eye on the burnt serated tip spreading too. p, k, s all are possible.. heck, k both tox or def can case issues.. if oyu see interveinal chlorosis then you can bring Mg into equation ... so... at this pointwait and see.. let it clearly present itself bc adding or removing something unrelated is often far worse. btw the green is algea.. it's harmless. light and moisture = inevitable algea.. this leads to questions about irrigation habits... which also could be related to that dead chunk off the leaf that is oddly rectangular (lol the insect/human et al part above).... i see from wet pattern you aren't saturating the pot. not doing so will cause add concentration gradients in the substrate, which has risks of leading to problems. fully saturate and wait until the coco starts to turn color or even top superficial layer is dry/lighter in color. it's coco, so i assume you have 'hydro' nutes, which means fully plany avaialbe, 100% soluble well-balanced diet at roughly 1.3-1.5 EC give or take relative to the plant at hand. Always fertigate. Always get at least 10% runoff waste water -- toss waste water outside or down the drain.. it is not for potted plants if you do that, you'll never have a root zone issue. won't get stuff growing on top of substrate, either. it also ensures a constant equlibrium is maintained in the substrate relative to nutrient concentration. be religious about that runoff, and you can more easily dial in your formula. early on it's better to be conservative about re-fertigation. it promotes deeper, larger root system (feast/famine cycle vs keeping it wet.. famine is a bit too strong of word.) - if you get superficial roots, especially early on and excluding a rootbound plant, it's 100% due to watering habits. i can stick a finger 1" deep into a pot with a 70 day old plant / 50+ days in the pot and not hit roots. By the time 12/12 flip comes around, or with an auto as preflowers come in, i do fertigate more frequently relative to loss of pot's mass, i.e. water-weight. the top layer won't be dry at all and if i get algea, so be it, lol. by that time the canopy keeps it dark enough that i rarely see any. algea require light to live (photosynthesis)