Fan leaves are turning yellow then brown

[woahtherelad]

Hello, this is my first grow and i have encountered a problem. The strain of the plant is jack herrer. About three weeks ago i changed the light schedule from 18/6 to 12/12. Previously, the plant was in veg for 49 days. Ever since I flipped it to flowering brown and yellow spots have appeared on the big fan leaves. Also, some but not many of the small fan leaves have turned yellow and brown and fallen off on their own. The last time i watered the plant was with a full dose of general hydroponics nutes and a gallon of water about two days ago. I ph the water to 6.5 every time i water the plant. I'm using ocean forest fox farm soil. The size of the pot is five gallons. The temps in the grow tent are 75 degrees and humdity is around 40%. I feel like it has nutrient burn since i recently went from giving it half dose of nutes to the full dose. I give nutes every other watering. The plant has a 150 watt led light. Any advice on what could happening or how to fix it?? Thank you!!

 

[Uno420]

Could be worth checking the roots for rot.
So this began before using your last dose of nutrients?

Do you normally get run off during / after watering or does it take and hold the full gallon?

Dont know the soil as not used it, but assuming it already has high nutrient levels, may be overdose or toxicity (especially if you are not getting any run off during water/feed)

Have you tried a flush with ph corrected water only?

Also is the pot drainage consistant? Do you have a way to check the moisture levels in the lower half of the pot before watering or is the plant showing signs of dehydration before watering?

 

[JohnDee]

Dont know the soil as not used it, but assuming it already has high nutrient levels, may be overdose or toxicity (especially if you are not getting any run off during water/feed)

As a general rule...never use full manufacturers reccomended dose. Most always too high. But luckily you've only given 1 dose. Not a soil grower now...but used to. I say no need for flush. Make sure you keep plant on good wet/fairly dry schedule and maybe feed 1/2 with at least one watering in between. Maybe wait two more water only waterings before starting back on reduced nutes.
JD

 

[woahtherelad]

Could be worth checking the roots for rot.
So this began before using your last dose of nutrients?

Do you normally get run off during / after watering or does it take and hold the full gallon?

Dont know the soil as not used it, but assuming it already has high nutrient levels, may be overdose or toxicity (especially if you are not getting any run off during water/feed)

Have you tried a flush with ph corrected water only?

Also is the pot drainage consistant? Do you have a way to check the moisture levels in the lower half of the pot before watering or is the plant showing signs of dehydration before watering?

I don't usually give the ENTIRE gallon but i mix the nutes with a gallon of water. I give maybe 80% of the gallon of water or i water until i see run off. I do normally get runoff every time i water. When i checked the ph of the runoff it was 6.5 as well. I'm leaning towards nutrient toxicity if I'm being honest. Before i watered with nutes i had flushed the plant with water that had a ph of 6.5. I think i should flush with ph'd water when the soil drys again?

 

[woahtherelad]

As a general rule...never use full manufacturers reccomended dose. Most always too high. But luckily you've only given 1 dose. Not a soil grower now...but used to. I say no need for flush. Make sure you keep plant on good wet/fairly dry schedule and maybe feed 1/2 with at least one watering in between. Maybe wait two more water only waterings before starting back on reduced nutes.
JD

Yea, i think I'm gonna start watering with only water. Do you think i should check the roots? or would that stress out the plant too much?

 

[Uno420]

You can gently dig down to check some roots, as its already in flower may stress it out if you pull the whole plant up, they should be white (ish) some nutrients and soil may discolor them slightly so dont be alarmed if they are a little off-white! Rot is fairly obvious usually.

Definitely worth a flush through and clean out any remaining nutrients in my opinion its more likely that, the soil has its own so deficiencies shouldnt be a problem anyway, personally Id do it sooner than later, as if it is toxicity it will continue to do damage while you wait for the soil to dry. If not worst case you will have slow growth for a few while it dries. Could be worth making a few extra holes at the bottom of the pot to aid the drainage, if you think it may be a problem drying?
If it is toxicity you should see a halt in further damage quite quickly. Id also leave all damaged leaves on for the time being as they are good indicators of further damage / fix / repair! Hope it works for you!

 

[JohnDee]

Yea, i think I'm gonna start watering with only water. Do you think i should check the roots? or would that stress out the plant too much?

You did say you only fed once, correct? I just don't see the need for a flush.
JD

 

[trambles]

Typically nutrient burn appears in new growth and literally looks burned.
I believe you have a calcium deficiency. When issues start in older leaves it's usually because the new growth is sucking nutrients from the old growth.
I would add cal mag and see if that stops the problem from getting worse

 

[woahtherelad]

Typically nutrient burn appears in new growth and literally looks burned.
I believe you have a calcium deficiency. When issues start in older leaves it's usually because the new growth is sucking nutrients from the old growth.
I would add cal mag and see if that stops the problem from getting worse

I thought it was a phosphorus deficiency at first so I added more nutes and the problem seemed to get worse? Do you think cal mag would fix it and would I just add the calmag with water or do I add the cal mag, nutes and water at once?

 

[trambles]

Calmag wont fix damage already done but IF it's the problem it will stop it from progressing.
Just add the calmag to your fertilizer mix and apply

 

[woahtherelad]

I bought the calmag yesterday so it should be arriving tomorrow. Do you think I should flush with just ph’d water, and then the next time I water add the cal mag or should I just water with the calmag tommorow?

 

[Uno420]

In my opinion its not a deficiency caused by feed/soil, as you are growing in a nutrient containing soil, plus the feed on top. That to me suggests and looks more like lockout, as the lower fans are being drawn from to create new growth agreed with trambles. Has new growth / flowering stunted since your original post?

My opinion, a flush is not going to cause you much further damage if the issue turned out to be a deficiency.
But adding further fertilizer to what MAY be a lockout due to overfertilization will likely only cause you more problems in correcting the issue.

What water are you using? And do you know the content of the soil from manufacturer?

 

[woahtherelad]

In my opinion its not a deficiency caused by feed/soil, as you are growing in a nutrient containing soil, plus the feed on top. That to me suggests and looks more like lockout, as the lower fans are being drawn from to create new growth agreed with trambles. Has new growth / flowering stunted since your original post?

My opinion, a flush is not going to cause you much further damage if the issue turned out to be a deficiency.
But adding further fertilizer to what MAY be a lockout due to overfertilization will likely only cause you more problems in correcting the issue.

What water are you using? And do you know the content of the soil from manufacturer?

I flushed with water that had a ph of 6.5 in hopes of the problem stopping yet i think I made it worse. It’s been two days since I flushed and the soil is still drying. Should I flush with plain water again or try the calmag this time? Yea the top fan leaves are now affected and it’s worrying me. Also if it is lockout how would I stop it from worsening?

 

[woahtherelad]

In my opinion its not a deficiency caused by feed/soil, as you are growing in a nutrient containing soil, plus the feed on top. That to me suggests and looks more like lockout, as the lower fans are being drawn from to create new growth agreed with trambles. Has new growth / flowering stunted since your original post?

My opinion, a flush is not going to cause you much further damage if the issue turned out to be a deficiency.
But adding further fertilizer to what MAY be a lockout due to overfertilization will likely only cause you more problems in correcting the issue.

What water are you using? And do you know the content of the soil from manufacturer?

Also I’m using tap water.

 

[HobbyGrowArtist]

do up a flush filled with micro-nutrients with a little magnesium/calcium, dolomite and epsom salt. drop ph slightly below 7.
then slowly water with same setup as flush except with regular macro-nutrients and secondary nutrients but with less than usual (just so plants dont starve and get worse).
should resolve in a week after this. could just be a hiccup during growth or something was off in the nutrients/ph.

after doing flushes and resetting nutrients prune the leaves affected except 2 or 3, do this a few days after first flush. just leave ones that are slightly affected and see if they get worse and see if healthy leaves get worse.