HELP! Can't identify issue with sick plant.

Hello! I’m currently growing three dutch passion white widow plants inside a 2x2 tent under a 120w led with a good exhaust and oscillating fan.

They’re in 3gal pots filled with coco, peat, worm castings, perlite and other amendments, and I’m using a local organic fertiliser which has always worked out perfectly from veg to flower in all of my runs.

Symptoms are limited to top/new growth: leaves discolouring from the tips, rust/brown spots in a few leaves, leaves canoeing/tacoing, slow growth.

I’m thinking this could be a sign of deficiency, but I’ve raised the fertiliser dose and it hasn’t really stopped. I’m pretty sure the watering schedule is fine since I’m relatively experienced and this isn’t something I’ve got wrong in a long time.

That aside everything looks good, so I’m stumped as for what to do to rectify this issue. Any help will be GREATLY appreciated! Thank you!

What lighting, and what are your temps and RH? The tacoing on upper growth is often a sign of too much light. Also could be low humidity, high temps, or all of the above. Looks like there may be a mg def starting as well but could be locked out if you raised nutes from your normal schedule which worked well in the past.

Hook Daddy said:

What lighting, and what are your temps and RH? The tacoing on upper growth is often a sign of too much light. Also could be low humidity, high temps, or all of the above. Looks like there may be a mg def starting as well but could be locked out if you raised nutes from your normal schedule which worked well in the past.

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120w led (quantum board with samsung lm301h diodes, running at full power 40cm/15in away from the canopy), humidity is on the high side... 77-87% daily. Temps are mild, 20-25ºC / 67-77F.

Magnesium deficiency. Early.

Looks like a magnesium deficiency, are you using cal-mag? Try a foliar spray of Epsom salt and see if that doesn't clear it up.

Thanks, everyone. I was suspecting it was some sort of deficiency, but was also thinking it could be light stress and/or nute burn. Will do a foliar spray with epsom salt and report back, in case anyone else stumbles upon this thread in the future.

pandaren11 said:

Thanks, everyone. I was suspecting it was some sort of deficiency, but was also thinking it could be light stress and/or nute burn. Will do a foliar spray with epsom salt and report back, in case anyone else stumbles upon this thread in the future.

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Do you reuse soil?

buckaclark said:

Do you reuse soil?

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I don't! I Always start with fresh medium.

pandaren11 said:

I don't! I Always start with fresh medium.

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I run DTW coco, don't know much about soil. How much coco in the soil mix? Maybe the coco is absorbing mag. Was it buffered? Are you aware of cation exchange? The cool temperature slows growth, low to mid 80's is best under LED.

Everyone, I'm sorry for the mixup. The medium I'm using has no coco. Its composition is as follows: 80% peat moss, 20% vermiculite + NPK traces, EC = 0,7. From that, I've added 10% worm castings and 18 grams of cockroach castings, 18 grams of mealworm castings and 18 grams of bokashi.