Newest leaves turning yellow

Hi everyone, I saw a miserable sight in my yard. The newest leaves are turning yellow of my plants moved outside 1 month ago!!! A few even died… those dead ones, either whole plant or branches, have burnt brown spots on the leaves. The pictures are attached below.
It’s have been over 30oC these days, so we water every 2 or 3 days thoroughly with 20-20-20 from MJ plant product. The whole yard seems developing in the same way. I am so upset and worried that all those with yellow tops might die.
SOS…Any clues of the cause? for the yellow leaves on every top and the dead ones with brown spots? Many thanks in advance.

Need soil info, and nutrient info (if giving them nutrients). If you have given them nutrients what ones and how many, if soil what kind? Looks like a few things, calcium, magnesium, and phosphorus deficiency. Have you giving them CalMag?

Looks like you have an iron deficiency. I’d find a product like calmag that has chelated iron and start adding some to your watering. It can also be used as a foliar spray for immediate help. Just wait until dusk or dawn to apply.

Thank you Bobby very much! I was suspecting overwatering, but confused with iron deficiency. Didn’t give calmag. bcz watered with well water and thought would be only too high not too low. Could be that too much calmag obstructed iron absorption. will give it a try if not better after a few days of draining.

Thanks for your reply! used BM6stand from Beger soil mixed with horse dirt. have been given only 20-20-20 from MJ plant product 900ppm since transplanted into big bag and moved outside. watered with well water rich in iron as I can see the reddish brown colour once a while from the water. watered every other day or 3 days whenever the top soil got dry even the underneath was moist. every watering was with the same nutes same ppm, without addition of calmag or any other minerals.

Don’t water so much. If the top of the pot is dry that is A Ok, cannabis actually like a period of dry and then water. Watch your leaves, if they are out and happy, no need to water. You might benefit from purchasing a soil moisture meter from you local farm store or Amazon if you can’t find one locally. You know how you stick a toothpick in a cake and if it comes out with some crumbs on it, you let the cake bake a little longer? Well, if you stick your finger into the soil a couple inches below the surface and it feels moisture or better yet you have moist soil on your finger when you remove it from the pot…Don’t water them. Watering should never be scheduled it should be done purely from observing the plant and soil.

Ok, are you saying that you fed them with a fertilizer that is 20-20-20?? If so that is wayyyyyy wayyyyy crazy hot. @MrPeat @Myfriendis410 @Hellraiser , would you care to jump in? The horse manure has lots of nitrogen in it so adding even more sounds maybe not so good, but I am just making an educated guess. Let’s see what these other great growers have to say.

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Yup…I concur. That 20-20-20 plus manure is gonna cause problems. You will more than likely end up with to much nitrogen and bam…a big hot mess.

From what others have said you really need to compost manure for a length of time.

Also…looks like the beginning stages of to much Phosphorus which causes the leaves to turn black.

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Many thanks to IslandGrown76 and MrPeat! I agree with both of your opinion. The plants are still young and the roots are soaked or even pickled with nitrogen and phosphorus, which might have caused the leaf problem. I am gonna leave the pot to dry and then water without any addition for a couple of time and see if the condition turns better.
Thank both of you for being there with great insight! :relieved:


That is why we are a great community. We want the best for each other. :+1: