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Home Forums Grow Community – Ask Questions & Share Your Grow! Yellow with brown/rust patches?

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    Hi everyone!

    We are new growers. We have been seeing yellow leaves with rust/brown patches. (see bottom of pic). These are showing up on the lower fan leaves. I tried to find out some answers on my own, but would you tell me what is manganese (Mn)? I thought it meant magnesium (Mg) (like cal-mag). We started nutes at 3 weeks old at 50%. Went to 75% and went full dose tonight. We are top watering with about a liter each. Gave 1/2 gallon with cal-mag 2 days ago and noticed a small amount of runoff. Are we watering too little? We are watering every 3 days unless dry. Our schedule is: water, water w/cal-mag, water w/other nutes…..(afraid of nute lock-out) We have analysis paralysis from too many you tube videos but we follow Mr. Grow It and The Stash podcast religiously. You guys are the best.

    What strain is it? Super Lemon Haze (also growing Purple Haze) both feminized
    Is it in Veg or Flower stage? Veg
    If in Veg, for how long? Week 5 starts tomorrow
    If in Flower stage, For how long?
    Indoor or outdoor? Indoor
    Soil, Soilless or Hydro? soil?
    If soil/soilless, what is in your mix? 60% coco, 20% worm castings, 20% perlite
    If soil/soilless, what size pot? 5 gallon fabric
    Size of grow space (LxWxH)? 60x60x80
    Make and model of grow light? AC Infinity Ionframe EVO8 5×5
    Light distance from the top of the plants? 18-20 inches set at 60%
    Temperature in the environment? set at 78
    Humidity in the environment? about 65-68 (set to VPD 1.1)
    PH of medium or reservoir? haven’t tested (ph water & nutes to 6.0)
    EC/PPM of medium or reservoir? haven’t tested
    Any Pests? No
    How often are you watering? about every 3 days depending on medium
    Type and strength of nutrients used? Cronk-micro, gro, bloom, cal/mag, monkey juice (we add cal-mag separately with water in between other nutes. We don’t add them all at once. See my post above. Super Yellow Haze


    Magnesium and manganese are 2 different elements. Magnesium is used in many different metabolic processes throughout the plant. Manganese is also important in small amounts, but it is not nearly as crucial.

    It seems like you are underfeeding. It specifically looks like you have iron deficiency. I suggest watering plain water and then feeding the next time and continuing this pattern (water/feed, water/feed, etc.), which should help prevent you from getting any lockout or toxcicity. You can either do calmag when you feed the nutrients or you can do it on the water only days. Most calmag also contains iron. You typically want to see about 15% runoff with synthetic nutrients. Regarding the brown/rust patches on the bottom canopy, that is normal for lower growth that isn’t getting enough light. The plant is reabsorbing the nutrients in those leaves.

    Iron Deficiency in Cannabis Plants


    Thank you. We thought we were not giving enough nutes and watering. We’re going to ramp it up a little. BrotherĀ  Minnejuana told us to turn the lights up to 70%. Says we’reĀ  babying the babies. Would like to see more growth. Do we get the girls healthy first, before going to the next level? Curren6 readings: Temp: 76.5 Humidity: 67.4 VPD: .098


    Yess, once you see the leaves return to a healthy green color you can turn your light up. Keep in mind that feeding is proportional to photosynthetic output. You can’t increase one without the other. You should always correct deficiencies before increasing light intensity.


    Think we have our feedings under control but I should have raised the lights and lowered the intensity. Now I think we’re burning the girls. Is it dumb to go back to 50% on the EVO 8? We’re 3 weeks from flipping to flower. Lights are about 20″ from canopy.


    <p style=”text-align: left;”>Based on the information you gave I’m not sure it’s the light. If you have a ppm/ec meter I suggest you do a runoff test and post the ph and ppm. Lowering light intensity is always a good idea when you have issues though. Sorry my initial response didn’t do the trick. Was there anything that you can think that happened before they started going yellow?</p>


    I was too anxious and increased the light to 80% before they were ready. We also just tried Recharge on 12/11 and let them get thirsty before watering again tonight with cal-mag. Everything else is dialed in with the controller to perfection. We still might not be giving enough water. We only see about 5-10% runoff. Question: Can we pour the runoff back into the growing pots? We usually just dump it out.


    You should dump it or feed it to other plants if you can.

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