Id guess its magnesium not phos, add a tablespoon in 5g and nutes and feed them, second guess is low ph. Will cause yellowing and necrosis, ph meters dont always work if not stored in solution.
Or put epsom salt in spay bottle for faster action. But feed in water too. Should get them greening up in a few days. Most city water is close to 7ph, can fluctuate. Nutes can lower it alot, might need a buffer possibly? Anaerobic environment can do this too, will lower ph too far.
Beginners should use higher consentrated nutes like 20x10x20 for grow, and 10 -31-20 for flower. One part and less bs. If using tap water add appropriate ppms of epsom salt about 1 third to 2 thirds of tapwater ppms. Works for me.7 parts peat to 1 part wormcastings plus molasses is only short on Cu l believe and does have some copper in it just not enough. But for all macros and almost all micros this is almost perfect mix.
My tap water is 300ppm aprox l add epsom up to 500ppm and nute from there to 700 or 1200 for bigger girls further along. Using pro mix hp m for years and swear by it. Always good to me. Innert medium so excellent for seedlings and add nutes when plants show you they need it. Ive had many not so good looking plants in veg do very well and green up during flower, l veg 24hrs. Need to as grow area in basement, concrete floor cools them too much so heating pads or up off the floor a bit helps.
Flower tent in living room so better environment. Front and center of pic is new addon from veg room, did better with the veg this run but 1 month from seed is as far as l will take them now, that one is same age as the smaller plants in tent, think l broke taproot tip repotting, was very slow but trying to catch up, vegging 2 months and l had no room to raise light anymore. My light has no dimmer, think a company like fluence would build it in for a 660w commercial model, and for the cost of these units, to veg under it l raised as high as l can and cut back veg hours to 16hrs, l never saw any slowup in them.
I know that lower wattage leds are good but to flower a plant l would go for full spec 150w which will cover a 2x2 area well. Same watts as 600w in 4x4 You might find your light lacking for flower, excellent choice for veg but need 35w per sq ft and up for really great bud structure, bc under 12 hr dli is hard to meet. I would love to see your plant flowering under that light, might do very well but think genetics will have final say, ld keep it closer as flowers develope , not sure about bleaching bc bars dont seem to do that, plus allow for airflow. And cover area very well and no real hotspots.
I hope l didnt go too far off topic and something in here helps you. Send pics if anything happens, go slow and dont do drastick measures, have fun growing as it should calm you not stress you out, is lemon or orange tree in back corner not sure which as roomy was drunk when planting.
Doing better under 12x12 than 24hr by far, only been up for a month and half growth has doubled compared to others. Most plants were about the size of front center when l flipped them, found immature plants still veg for however long they want, will wait 45 days next or until they show sign. Her sis to the right in 8 gal nursery pot doing very well imo.
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