Mag/Pot Deficiency? Need some help

You guys helped me get these started in a previous thread “Three Weeks Old and Going Nowhere” and all had been going well. Plants are now 5 weeks in veg and are showing some problems. I checked photos of nutrient deficiencies and it looks like a mag or potassium problem. I’ve attached a support ticket as well as photos of some typical leaves exhibiting the symptoms. Help me out guys @Majiktoker @garrigan62 @Niala

Strain; ILGM White Widow Fem

Soil in pots: FFOF

PH: Watering typically w/rainwater pH @ 6.6

What is strength of nutrient mix? Have been using CalMag Plus @ 1/2 stg.every few waterings. Gave first lightr dose of FF BB GB 4 days ago.

Growing Indoors

Light system, size? CFL (17) 23 true watts (391 total watts over three plants)

Temps; Day, Night: Avg. 79/71

Humidity; Day, Night Avg. 45%

Ventilation system; Yes 6" exhaust

AC, Humidifier, De-humidifier: No

Co2; No

Plants need water today but wanted some input from you guys before proceeding.

Thanks, EE

Hey bud my experience with the ff trio is calmag is a must and I found full strength to be needed with my last grow I found my gorilla glue was just hungry for calmag and ate it up like crazy
Also I’ve heard other with the same situation when using ff trio just a FYI on my experiences
Happy growing

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@ErnieX is the yellowing starting from inside and spreading outward

Thanks @Countryboyjvd1971 @Majiktoker Yeh, looks like it starts close to the center vein and moves outward on the leaves. Also showing tiny brown spots that develop into brown areas as shown in the picts.

You may be having a sulfur deficiency and potassium deficiency

@Majiktoker How would you suggest I proceed? Can feed with FF Trio for potassium but I see it contains no Sulphur. Also throw in some CalMag for good measure? Forgot to mention also seeing lots of purple stems if this helps.

Red stems would rule out potassium there for being said yes cal mag and phosphorus which the ff trio contains you should be good to go

@Majiktoker @Countryboyjvd1971 :+1::+1:

I use this a lot. It helps greatly in figuring out the plant’s problems.

Thanks @TxGrowman Excellent reference.:+1:

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Below you’ll see why it’s a calciun deficiency i have added pic’s to show you and your solution for it.
I hope this helps


Solution For Calcium Deficiency in Cannabis

Your cannabis plant may show signs of a calcium deficiency if the pH at the roots is too high or too low. That is because when the pH of your root zone is off, your cannabis cannot properly absorb calcium through its roots. Therefore the first step is to ensure that you have the correct pH for your growth medium. Learn more about pH and cannabis.

Please note: After a calcium deficiency is cleared up, the problem (brown spots and unhealthy new leaves) will stop appearing on new growth, usually within a week. Please note that leaves which have been damaged by a calcium deficiency will probably not recover or turn green, so you want to pay attention to new growth for signs of recovery.

In soil, calcium is best absorbed by the roots in the 6.2 - 7.0 pH range (in soil, it's generally recommended to keep the pH between 6.0 - 7.0, but calcium specifically tends to be best absorbed above 6.2)
In hydro, calcium is best absorbed by the roots in the 6.2 - 6.5 pH range (in hydro, it's generally recommended to keep the pH between 5.5 - 6.5, but calcium specifically tends to be best absorbed above 6.2)

If you suspect your growing cannabis plant has a calcium deficiency, flush your system with clean, pH’d water that contains a regular dose of cannabis-friendly nutrients that includes calcium. This will remove any nutrient salts that may be affected the uptake of calcium and help restore pH to the proper levels…

To supplement with extra Calcium… (it’s very rare to give a cannabis plant too much calcium, however, too much calcium can lock out other nutrients so don’t go overboard)

Calcium, magnesium, and iron deficiencies often appear together in cannabis. Many growers decide to purchase some sort of Calcium-Magnesium (often called Cal-Mag) supplement for their grow room in case this common deficiency appears.

Listed below are common cannabis Calcium supplements, along below with some general information about each one. After supplementing with Cal-Mag and correcting the pH, you should expect to see new healthy growth within a week. Remember, the old leaves will probably not recover, but new growth should be green and healthy.

Cal-Mag is Well Suited For Hydro, Coco Coir, or Soil

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@garrigan62 Thanks so much for taking the time to provide the very informative response. The photos look very much like the problem I’m having. Prior to you response I watered the plants in three gallon pots with a gallon each of nuted and pHed rainwater. 1/2 strength FF Big Bloom and Grow Big per the published chart for week 5 as well as 1/2-3/4 strength CalMag dose. pHed in at 6.65 and runoff at about 6.5 with at least 20% runoff. I’ll keep an eye on the new growth and hopefully will see improvement. Yours and the others knowledge and assistance is invaluable. :slight_smile::v:


@garrigan62 @Majiktoker Fed the girls three days ago as described above per @garrigan62 recommendation. Plants perked up great and were looking good. Looked at them this morning and the new growth is showing brown areas as can be seen in the pictures. Any thoughts on what’s going on? Any assistance is greatly appreciated.


how close are your lights. looks to bbe light burn. move your lights up a bit.
best way to check tis is to place your hand under your light. if your hand feels uncomfortble so does your plant.