yellowing leaves between veins

the yellowing leaves are happening from the top ,not bottom . all of my 20 plants in such condition.
my grow medium is half coco and half earth worm casting. one 600w hps. i sometimes spray the nutrient on the leaves during the light on. often in the morning. is that possiblem it is the cause. they are 40days in flowering cycle. this proble did not happen to my last harvesting. last time . it just yellowed from the bottom which is normal for flowering stage. but this time . its between the vein from the top.

thanks man , indeed i did not rinse the coco very properly than the last time . i think thats why it did not happen that time. im gonna pay attention to this cause from now on

What he said↑. You could also check your runoff. Salted coco will have a very low ph plus high tds. Flush with 3 times the pot volume

vostok said:

I bet you didn't rinse out that coco when you unpacked it...No? as many suppliers claim it is washed but it ain't not by western standards at least, something to note for future grows, look close at that leaf you see that standard nute burnt panel but also slight yellowing in the veins themselves, have you been feeding RO water...? non the less an immediate flush and on the last rinse add some Calmag or Epsom salts 1 tsp. per us gallon is good

to my blog: https://www.rollitup.org/Journal/Entry/flush-baby-flush.27513/

Click to expand...

dude why would you add salt after rinsing salt!? there are more efficiant ways of getting cal mag than this. also with one leaf its hard to asses can you picture of the whole plant? why do you have 20 plants competing for 600w? that actually may be the sole problem plants get pissed when that happens and the nute levels go "fuckey" (trailer park reference). factor a 150w minimum per plant and you will get better results. on the subject of not washing that is also a possibility. i have been rinsing the same cocoa for years now and can offer some help. first get ppm meter and get it down to a 100ppm run off or so (it may be higher if your rinsing with extremely hard water so check what your starting with?) for more efficiency i agitate my cocoa by aggressive stiring it while it s being rinsed. doing this i get the ppm lowered way faster than just a plain rinse. lastly and very important pasteurize your cocoa at the end and let it cool before planting to keep pests at negligible level, before this it felt like i was always battling bugs but since i started these practices combined with precautionary occasional treatments with neem in veg i am producing a more consistent reliable crop then ever with way less shit to stress about. btw last time i grew 20 plants it was under 4k watts in a 10'X20'[ room greast results (see my sig). let your plants fill out dude you wont regret it! happy growing...oh yeah after rinsing check the ph of the run off, if its to acidic add dolomite to raise the ph back up to 6.8 or so this will also reduce the need for cal mag as a bunus providing a more stable growing medium.

oh almost missed it! foliar feeding has its downsides especially with the lights on. if you do it at high light levels and temp its going to burn. dont foliar feed flowering plants. feed from the roots thats what they are there for. there is good chance that is your true problem but it seems like you might have a few issue that will be a problem no matter what