Is this a burn or a deficiency?

[BigZX]

This is my first grow, and am not sure what the discoloration is from. Let me know if I need to give more information. Thanks in advance.

 

[mysticepipedon]

It's a deficiency. It might be early Mg or potassium — not sure.

 

[ezenzyme]

Want some trouble shooting done? Do tell!!!

1. Are you growing from seed or clones?
2. How old are your plants?
3. How tall are your plants?
4. What size containers are they planted in?
5. What is your soil mix?
6. How often do you water and what type of water do you use?
7. What is the pH of your water?
8. What kind of fertilizer do you use and what is its NPK ratio?
9. Do you foliar feed or spray your plants with anything?
10. What kind of lights do you use and how many watts combined? (HPS, MH, fluorescent, halogen, incandescent "plant lights")
11. How close are your lights to the plants?
12. What size is your grow space in square feet?
13. What is the temperature and humidity in your grow space?
14. What is the pH of the soil?
15. Have you noticed any insect activity in your grow space?
16. How much experience do you have growing?

to really understand whats going on and not be guessing we need a bit more info.....

 

[BigZX]

To me it looks like a magnesium deficiency since there is redness in some of the stems. However, there are two plants in the tent and the other doesn’t show any of the same symptoms. I’m using tap water until I get an R/O system so I haven’t added any cal mag yet.

 

[BigZX]

1. Clones
2. Around 5 weeks old
3. About 15 inches tall
4. 5 gallon containers
5. Nectar for the gods soil
6. Watering once a week with tap water
7. Water is ph adjusted to around 6.4
8. Sensi grow nutrients 3-0-0, 1-2-6
9. I don’t foliar feed or spray
10. 100 watt Spider farmer sf-1000 led at about 60% power
11. 28 inches away from plants
12. 5 square feet of growing space
13. 76 degrees at 50%rh
14. Soil tester says soil ph is about 7.5
15. Haven’t noticed any insect activity
16. First grow- no experience at all.

 

[coherent]

I'm not a soil expert, but if I had the same condition in coco/hydro my guess would be to up the Phosphorous and Potassium. Mostly feed them something with more P than the nutes you are using. Some soils lack sufficient amounts of necessary nutrients to sustain cannabis properly. Without specific soil ingrediants it's tough to know whats what. I looked the soil up and seems they have a number of blends, some are coco for hydro so definately require proper nutes and cal-mag. At that age, you should have no issues running your light at 100% at 18-24 inches. Eventually feed some cal-mag also.

 

[visajoe1]

do not need cal mag in soil when using tap water.

 

[BigZX]

I'm not a soil expert, but if I had the same condition in coco/hydro my guess would be to up the Phosphorous and Potassium. Mostly feed them something with more P than the nutes you are using. Some soils lack sufficient amounts of necessary nutrients to sustain cannabis properly. Without specific soil ingrediants it's tough to know whats what. I looked the soil up and seems they have a number of blends, some are coco for hydro so definately require proper nutes and cal-mag. At that age, you should have no issues running your light at 100% at 18-24 inches. Eventually feed some cal-mag also.

I’m using their #4 blend.

So far, I have only fed them once. Two weeks ago. I was afraid of burning them up if I fed them too early. Could that have something to do with it? I plan to add to possibly add some cal mag to correct it. I haven’t given it to them yet since I’m using tap water and figured there would be enough already. I just think it’s odd that both plants aren’t showing the deficiency, just the one.

 

[BigZX]

do not need cal mag in soil when using tap water.

That’s what I thought too.

 

[coherent]

do not need cal mag in soil when using tap water.

It's extremely unlikely that any problems will be caused by feeding some cal-mag. On the other hand if it's a coco based soil (based on the original OP limited info) it would definately be required. Also you must know more about the location and specific tap water info as far as where in the world the op is and if it's well, city etc. and specs than me. True most contain some levels of calcium and mag, but how much and what levels is an unknown. There are places where tap water quality can definitely be lacking.

 

[ezenzyme]

armed with the info i am still not to sure, your PH could be dropped down to around 7.0 or 6.9 cannabis likes slightly acidic soils. You can drop it down by watering with a lower PH water.
Is your soils tester one of those thingys that has three metal prongs and is supposed to be accurate? Those things are totally crap!
You need to do a slurry test on the dirt and then do a water to run off test and PH before and after. Run off and slurry test info should be easy to find on here

 

[SntWick]

Hope this helps

 

[BigZX]

Thanks for all the great information. I’ll add some cal mag with my next watering and do a runoff and slurry test.