Week 6 flower tops curling up help

Hi my plant is overall healthy but recently noticed the leaf tips are curling up. Is this from nutrient burn? Or start of a lockout/deficiency?

Growing in coco. Using h3ads method 6/9 micro/bloom with ro water. Ec 1.6, ppm 700-800. Watering daily till 20% runoff. In a 4x4 tent with 315cmh about 2 ft above canopy. Day time temps 72f, night time 65f. Humidity 35-45%. Have air flowing in bottom and exhaust taking air out the top. Have oscillating fan.

My guess is it’s nutrient burn and getting worse? 1 feed ago I stopped with the micro and just doing 10ml bloom since I’m nearing week 7 of flower. And adding 2.5ml GH cal-mag. To get .4 ec and 400ppm. So I’m hoping the lower ec will help them come back to normal.

I am also confused because I read a lot of forum posts saying don’t worry about run off ec in coco that it doesn’t matter... but then have read from a few articles other places saying the run off ec does matter if it’s significantly higher than the water going in and to try to keep what’s coming out 200 points within range of the inflow .( https://www.cocoforcannabis.com/managerunoffec/ ) Which my runoff ec was 3.3 and ppm 1671 which indicates salt build up if that’s the case.

Any help would be appreciated thank you

Beautiful, but they look like they might have a bit too much N to me. I'm no expert at diagnosing nute issues though.

Mild heat stress is all I'm seeing. The leaf margins stick up like that when the leaves are trying to cool themselves. Lower ones aren't doing that and overall it looks real good. When they are doing that tho they are pulling more water up there for evaporation to cool so will also pull more nutes up with the water then the tips along the margins will start going yellow/brown as the excess salts burn them.

I'd cut the ppm way back now to 400 or so and flush a bunch thru to get rid of any buildup. They're not eating a hell of a lot at this stage and just fattening up buds. Aim for lower N and P but keep some K going. Some Epsom salts is good too at about a tsp/gal or more for extra Mg and S.

It's most likely radiant heat from the light(s) and blowing more air across the tops will actually make things worse so if you can I'd raise the lights another 4 - 6" and see if that doesn't help.

It's not bad at all tho. Lots of sugar on that girl too!

Awesome thank you!! I moved the lights up some more and will definitely continue with that 400ppm and make sure I give it a good watering. My first time in coco so the whole salt build up thing kind of scares me. Lastly when I add the Epsom salt with my current mix (10ml bloom, 2.5ml calmag) it takes me up to 1.8 ec and 900ppm... is this a problem or since it’s just Epsom salt it won’t cause many problems?

Oblivi0us said:

Awesome thank you!! I moved the lights up some more and will definitely continue with that 400ppm and make sure I give it a good watering. My first time in coco so the whole salt build up thing kind of scares me. Lastly when I add the Epsom salt with my current mix (10ml bloom, 2.5ml calmag) it takes me up to 1.8 ec and 900ppm... is this a problem or since it’s just Epsom salt it won’t cause many problems?

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How many liters or quarts is that going into? Seems a little high yet but should be all right.

OldMedUser said:

How many liters or quarts is that going into? Seems a little high yet but should be all right.

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It’s going into 1 gal or 4 quarts. The tsp of Epsom weighed 1 gram in weight.

Oblivi0us said:

It’s going into 1 gal or 4 quarts. The tsp of Epsom weighed 1 gram in weight.

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I just weighed 1 level tsp of Epsom salts and got 4.4g on a good 0.01 digital balance. 3.37g actually but I rounded up.

10ml/gal is what I would consider a high dose this late in flowering and works out to 2.5ml/L. Even at the most vigorous growth levels I rarely go over 2.0ml/L with my AN 3-part and that's every 2nd watering. I rarely have any runoff to remove either as I try to feed on the low side unless the plant is telling me it needs more.

Most of the guys growing in coco say they water a few times a day and never let it dry out like I do with the peat based ProMix HP. I water until saturated then let it dry down until the pot feels really light but the plant isn't drooping yet. I have a Hindu Kush in a 7USgal pot at day 55 now and it takes 7 - 8L every 4th day or almost 2USG. Yesterday it just got a tsp of Epsom and one of Carbo in it's water. Changed my 600W Hortilux out for a brand new 600W 7200K MH conversion bulb too to see if it hastens the clouding of the trichs and should have higher UV light too to hopefully boost the THC a bit. Nice strain a buddy gave me a cutting of a year ago. The plant goes dark purple the last few weeks and smells so nice while trimming fresh and even better after curing. I want to cross this one with my hi-CBD plants and make fem seeds.