The whole plant is yellowing

Blackketch

Active Member
Hello, a strange thing is happening to me in my grow room ... basically one of my 4 plants (same strain, same soil and same water) has become completely a very bright light green color, almost yellow, and I started to notice purple veins between the leaves. I just can't understand what it is due to since the others are pretty strong and healthy. I specify that the plant in question has always been the slowest and most precise also that it is my usual not to fertilize in the vegetative phase since I use the royal mix of plagron which has always covered me 6 weeks of vegetative calmly with really excellent results.
My setup:
Grow Box: 120cm × 120cm × 200cm
Air inlet and extractor
Airpot vase
Led light: Mars Hydro Tsw 2000
Soil: Plagron Royal Mix
PH: 6.5
Plant age: 30 Days (from seed)
Techniques: Topping
Watering frequency: Every 2 days 1.5lt per plant
Rh: 55/50% Temp: 23 °
Light distance: 38cm dimmed to 50%
I'm at work at the moment and can't take pictures but I'll post them later. I already know that it is definitely a nitrogen or magnesium deficiency but I don't understand how this is possible since the plants are all treated equally.
I have only recently used spinosad on the leaves
 

Blackketch

Active Member
@bam0813 rightly it makes sense what you say but such a thing has never happened to me .. since I use this method of the royal mix for 6 weeks, I have never had such problems that usually occur with ph fluctuations because it just seems that unable to absorb the nutrients of the pre-fertilized soil and I repeat that all the others are just fine! I water them only when the surface of the soil dries up and I increase the amount of water based on how many days it takes before they absorb most of the previously poured water. At the moment I go to normal tap water and when I start flowering and start with fertilizers (Advanced Nutrient) I use purified water with reverse osmosis.
 

OneMoreRip

Well-Known Member
ph of what is 6.5? If not the medium, what is the ph of the medium?

also pictures are helpful to those who would try and help you
 

OneMoreRip

Well-Known Member
@OneMoreRip the ph of the soil is 6 / 6.5 and the ph of the water is always 6.5 however as soon as I get home from work I immediately post some photos
sounds good, i'd compare the good ones with the bad one, regarding everything you believe may be relevant and you may find your problem. my only guess would be ph, assuming it has same feed as the others. maybe over watered if getting same waterings as others and you said it was smaller smaller.

ive never seen anything saying one cannabis plant has different than standard requirements for good health, but if someone has a link to info on that, I'd love to see it. Thanks
 

bk78

Well-Known Member
sounds good, i'd compare the good ones with the bad one, regarding everything you believe may be relevant and you may find your problem. my only guess would be ph, assuming it has same feed as the others. maybe over watered if getting same waterings as others and you said it was smaller smaller.

ive never seen anything saying one cannabis plant has different than standard requirements for good health, but if someone has a link to info on that, I'd love to see it. Thanks
Another full night of no sleep I see.
 

twentyeight.threefive

Well-Known Member
sounds good, i'd compare the good ones with the bad one, regarding everything you believe may be relevant and you may find your problem. my only guess would be ph, assuming it has same feed as the others. maybe over watered if getting same waterings as others and you said it was smaller smaller.

ive never seen anything saying one cannabis plant has different than standard requirements for good health, but if someone has a link to info on that, I'd love to see it. Thanks
Every single plant issue is pH, huh?

Coming from the guy that sticks his liquid pH tester in his soil.
 

Blackketch

Active Member
IMG_20211123_135551.jpgIMG_20211123_135610.jpg
IMG_20211123_135838.jpg
these are the photos in comparison with the rest of the plants inside the box. however he never gave me a sign of overwatering, or at least I think I never noticed anything strange, but as you say I thought it was a problem related to the ph.
 

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OneMoreRip

Well-Known Member
Not sure how you checked you medium ph, but I’d double check and compare with you good plants.

also from your soil. “When using Royal Mix, you can expect a period of 3-6 weeks after each transplant before using liquid fertilizers, depending on the volume of the pot used (the bigger the pot, the more nutrients will be available for the plants).”

so it may need fed now.

A lot of purpling stems, always happened to me from ph lockout.

if needs food, I’d give something near 2-1-2 or whatever you normally use that works for you.

Not sure Epsom salts is good for much from my research
 
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JimmiP

Well-Known Member
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these are the photos in comparison with the rest of the plants inside the box. however he never gave me a sign of overwatering, or at least I think I never noticed anything strange, but as you say I thought it was a problem related to the ph.
I would check the soil temperatures. The first picture in this series you posted shows what seems to be an air inlet pointed directly at the airpot for the troubled plant. That colder incoming air could be significantly lowering the rootzone temperature and causing problems with magnesium and phosphorus uptake. I would try to redirect that inlet tube away from the pots.

I would also lift all of them off the floor a few inches. The floor can act as a large heatsink, drawing warmth away from the medium.
Hope this helps.
Good luck friend!
 

Blackketch

Active Member
@OneMoreRip I checked the pH by taking a sample of earth and mixed it with water with neutral pH and I added 3 drops of liquid tester and, since the water was a bit cloudy, I couldn't define from the color if it was a 6 or 6.5 however for sure between a range of 6-7. the plants were transplanted 2 weeks ago in 17lt pots but in the meantime I will try to feed only the plant in question. Tonight I will check the ph pot by pot and update you!
 

Kushash

Well-Known Member
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these are the photos in comparison with the rest of the plants inside the box. however he never gave me a sign of overwatering, or at least I think I never noticed anything strange, but as you say I thought it was a problem related to the ph.
Seeds are like brothers and sisters and some seeds might not be as vigorous as others, some might be Mg whores.
If it was my plant I'd take it away from the light and give it a foliar with 1/2 Tsp of epsom salt per gal of water and water some in the next time you need to water it. If it's Mg the plant will show an improved color about 4 days after being treated. I favor it being a Mg deficiency over N.
 
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