how to fix magnesium / potassium deficiency on autoflowering plants?

moogie_

New Member
This is my first grow, still learning a lot but thought i'd come here for help from more expirienced growers. any and all help greatly appreciated. As far as plant info goes, the two plants in the back of the tent are thc bomb autos from MSNL and the front one is a white widow auto also from MSNL, all planted in coco with perlite and are currently on week 8 / week 3ish of flower. I recently moved them into a new tent because the nodes were growing into my hps light (ik thats bad for them i ran out of space and was waiting on the new tent). I am mainly unsure of what to do right now because these various issues and leaf patterns could be a lot of issues. for starters some of the nodes that grew into the light have burnt leaves around the buds but then also yellow/yellowing leaves that have red stems on the affected leaves. I topped once around week 3 and did lst once in week 3 and once again before switching to the bigger tent last week and defoliated once in late veg and once around week 6. I also believe i was overwatering a bit and noticed the plants were drinking less since flowering (is that normal?) so I switched to watering every other day which the plants seems to be okay with. Additionally, when i moved the plants into their new tent i turned the hps up from 250w to 600w (i have one of those dimmable ballaststs) and made sure to keep the plants about 14-18in from the light (i did this because i read that the more light the better but idk if its bad for them rn). for nutrients ive been using the GH flora series micro, grow, and bloom with some calimagic for ca and mg. Looking online i believe the issue is a magnesium deficiency because that can also cause potassium deficiencies. I saw people talk about adding epsom salts to their water to help with the mg deficiency. I also saw people talk about watering gypsum into their soil to also fix this issue. Basically just asking if anyone can vouch for these methods or recommend any that worked for them.IMG_4288.jpeg
 

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MickFoster

Well-Known Member
They look fried to me.......there could be any number of reasons. More info about your grow is required.
You might consider flushing the crap out of the coco with a mild nute solution using a pH around 6,0.
Then start feeding twice a day to substantial run off, using a ppm around 600.
You can't over water coco with a plant that size.
 

coreywebster

Well-Known Member
Could be light burn, could be lock out.

Mg def shows low down and works up
Light burn shows up top.

Might be they got shocked and stopped drinking and as a result you started feeding every other day causing salt build up and lock out.

I'd treat it that way and do as Mick says because there's no harm in doing that and it might solve the problem.

If you've got a tds meter you can test the run off and see. If not you can just assume its high EC and flush.

Then get to watering every day with 10-20% run off.

You don't say how many hours of light you are running or give environmental conditions and the pics are hard to judge due to the hps light.

So there's some theories to explore
 

moogie_

New Member
They look fried to me.......there could be any number of reasons. More info about your grow is required.
You might consider flushing the crap out of the coco with a mild nute solution using a pH around 6,0.
Then start feeding twice a day to substantial run off, using a ppm around 600.
You can't over water coco with a plant that size.
hello I just did this for watering today using my nutrient chart(week eight). I also checked the ph of the runoff water and it came out as yellow / 5.7-6.0ish (i am using a water ph tester in a vial with indicator so i cant be 100% exact). one question tho, when you say water twice a day do you mean with nutes or just phed water? also when would you recommend doing so during the day? (i have just been watering in the morning around 8am ish before lights shut off at 130pm.) I have also been giving plain phed water everyday and should i flush with that or just nutreint water? tysm
 

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moogie_

New Member
Could be light burn, could be lock out.

Mg def shows low down and works up
Light burn shows up top.

Might be they got shocked and stopped drinking and as a result you started feeding every other day causing salt build up and lock out.

I'd treat it that way and do as Mick says because there's no harm in doing that and it might solve the problem.

If you've got a tds meter you can test the run off and see. If not you can just assume its high EC and flush.

Then get to watering every day with 10-20% run off.

You don't say how many hours of light you are running or give environmental conditions and the pics are hard to judge due to the hps light.

So there's some theories to explore
so you dont think its mg def? mb for not being more specific i have been giving these plants 18 hrs on and 6hrs off for the entirety of the grow. for temps usually the tent is around 72-80 degrees F with a humidity of ~45%. I am attaching more clear photos here which i hope helps. as for lockout i checked run off ph today for the first time and got yellow for all three plants (about 5.7-6.1) ph. So does that mean theres no lockout? I will also attach the feed schedule i am using bc i suspect the amounts for calimagic are too low (week eight but idk). when i looked at the plants today i saw the yellowing affect still spreading and some new spots developing on a few leaves (also stems look a bit redder).
 

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coreywebster

Well-Known Member
hello I just did this for watering today using my nutrient chart(week eight). I also checked the ph of the runoff water and it came out as yellow / 5.7-6.0ish (i am using a water ph tester in a vial with indicator so i cant be 100% exact). one question tho, when you say water twice a day do you mean with nutes or just phed water? also when would you recommend doing so during the day? (i have just been watering in the morning around 8am ish before lights shut off at 130pm.) I have also been giving plain phed water everyday and should i flush with that or just nutreint water? tysm
Always use nutes with coco.

Read this

 

MickFoster

Well-Known Member
hello I just did this for watering today using my nutrient chart(week eight). I also checked the ph of the runoff water and it came out as yellow / 5.7-6.0ish (i am using a water ph tester in a vial with indicator so i cant be 100% exact). one question tho, when you say water twice a day do you mean with nutes or just phed water? also when would you recommend doing so during the day? (i have just been watering in the morning around 8am ish before lights shut off at 130pm.) I have also been giving plain phed water everyday and should i flush with that or just nutreint water? tysm
Never, ever give coco plain water.......always with nutes to run off.
I feed when they wake up and again 1/2 way through their light cycle.
 

moogie_

New Member
Never, ever give coco plain water.......always with nutes to run off.
I feed when they wake up and again 1/2 way through their light cycle.
i see i see, so i should just keep to my current schedule but skip plain phed water til flush, and water to 10-20% runoff 1-2x per day. makes sense, ty. do you think that would fix the issues with the leaves?
 

moogie_

New Member

zem

Well-Known Member
Flush them and feed with no Nitrogen and plenty of PK. Feeding only salts can cause issues. Next time start using amino acids and biostimulants like kelp and microbes to help the roots uptake nutes, and start cutting N early in flowering.
 

moogie_

New Member
Flush them and feed with no Nitrogen and plenty of PK. Feeding only salts can cause issues. Next time start using amino acids and biostimulants like kelp and microbes to help the roots uptake nutes, and start cutting N early in flowering.
so should i just take flora micro out of the equation and continue with my current feeding chart as is? I think flora grow has some nitrogen in it too. fs tho wanna use more biostimulatnts / amino acids in the future / next grow if you have any recs
 

MickFoster

Well-Known Member
so should i just take flora micro out of the equation and continue with my current feeding chart as is? I think flora grow has some nitrogen in it too. fs tho wanna use more biostimulatnts / amino acids in the future / next grow if you have any recs
I know you didn't ask me, but the micro should always be used. You can get by without the grow and just use the micro and the bloom.
 

zem

Well-Known Member
you need the micro nutes that are in the micro but not the N, which is why i don't use it in flowering. Some flowering runs I need a low dose of N late in flowering, other grows when plants are greener like yours, I cut it out almost entirely by this time through. The last source of N I cut is that of amino acids AA because I want their other benefits, so I go with the lowest N Amino. I have 3 or 4 types of AA that range from 6 to 11% N. Also Kelp and higher calcium do wonders along with mycorrhizal inoculants, you will have the plants thanking you. Simply adding calmag is the thing most unprofessional growers resort to when they see such problems, however it is way more likely that they have an imbalance rather than a deficiency. The low levels at which I feed Mg were never conceivable before I learned how to balance my feeding. You need to learn what ratio of NPK Ca MG S Fe etc you need at every stage of life and calculate all the elements you are adding.
 
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