Is this mold or a deficiency?
Looks like a deficiency to me, you can tell by your leaves are “clawing”.
I’m not good with diagnosing deficiencies, but if you fill out a support ticket, guys like @garrigan62 and @Majiktoker are amazing at diagnosing problems with nutrients.
I hope that it is…hey how did that topping at the 3rd node work?
Dose this look simular.?
Yellow leaf spot, also known as leaf septoria, are caused by Septoria cannabis and S. neocannabina. These are fungal pathogens aimed specifically at marijuana plants.
It is brought about by warm weather and rain and effect marijuana grown outdoors. It may also show up in nitrogen- deficient plants. Read this article and learn how to identify and treat yellow leaf spot.
Signs of leaf septoria
Signs of leaf septoria weed
Yellow leaf spot initially shows up on the lower leaves of your plant. These spots may vary in shade from white to a grayish brown to yellow, initially displaying little circular lesions. Once it starts to grow it starts looking like a bump and its size continues to increase.
Yellow leaf spot will harm the leaves and often times the stems of the plant, although it won’t cause the crop to die off. If for any reason this is not properly cared for it will lessen the marijuana plants yield. The affected leaves will become dry where the spot is and overtime break and produce a hole at the point where the spot started off.
Not sure if your marijuana plants suffer from a yellow leaf spot infection? Check the article Marijuana diseases for a list with pictures of all possible marijuana diseases
How to avoid and cure leaf septoria
Cure yellow leaf spot cannabis
The most affected leaves will become totally yellow, dry out and fall off. You will want to get rid of the leaves that fell off or else you will end up with a landing turf for spores to overwinter. Basically, they will hide out until the weather warms up and then that’s when they will wreak havoc. Yellow leaf spot spores do their dirty work through traveling by water, wind and clinging on to things that pass by.
You can avoid the damage yellow leaf spot causes your plants through crop rotation. Basically, after every harvest you will pick a new location to plant. If you are not able to do this, then after harvest, completely get rid of all leftovers from the last vegetation and till the soil really good to make sure all remains are gone.
Download my free marijuana grow guide at this link for more growing tips
Get the location ready using sterilized compost and mix it well into the soil. Doing this will give the new crop plenty of nitrogen to provide a good, strong start. If you don’t have any ready compost, you can mix in blood meal, fish meal or soybean meal to the dirt that is already there.
Therefore, you will be certain to have all the necessary nitrogen for your plant. Make sure you proper disinfect any tools you used with rubbing alcohol or peroxide prior to putting them away.
One more thing you can try when beginning a new marijuana bed is adding a fungicide to the planting location prior to putting the seedlings and seeds there. You have the option to buy one of the many natural solutions pre-made (at this link here) or you can make your own.
Applying helpful bacteria, like Bacillus Pumilis or a good fungi like Trichoderma will help the soil if you don’t have any compost to use. Also, you may try spraying the site with essential oil combinations with cinnamon, coriander, neem, sesame or clove. Fine misting the soil with compost tea or even baking soda will aid in avoiding yellow leaf spot spores from making a home at your site.
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Marijuana plant symptoms
– white/grayish brown/yellow spots on leaves
– Circular lesions on lower leaves
– A small pimple looking bump
– Leaves dry and fall off
Remember to water your plants early mornings or early evening time. Never water the leaves, only the soil. By doing this, the sunlight will not burn the leaves. Again, if your plants gets infected by yellow leaf spot, it is important to always remove and completely destroy all affected leaves.
If you don’t do this, you will most likely regret it. Affected leaves still contain the problem and can come back to haunt you because yellow leaf spot easily clings on to things and travels from one destination to the next.
Remember that plants with strong genetics have less change of getting sick and are less vulnerable for pests and diseases. So make sure to buy cannabis seeds from a trusted seed bank.
Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible
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Writen by Robert B.
Posted by garrigan62
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Seems to be a lot of this going around ?
I’m dealing with this too and I got my information from will garrigan as well
so far 1 spray of neem oil and sodium bicarbonate twice and I’ve almost completely stopped it
get on this fast because this damage will spread like wildfire and I’m not exaggerating
If I can answer any more specifics just let me know but I am sure Will has it covered above and I have a thread on this as well, when I get a second I’ll drop a link
-good luck bud
@Paranorman as it stated above have you disposed of all the bad leafs.
Oh ! that’s all I do is throw leaves away! …that’s how I noticed it kinda stopped
It’s become like a day job …its interfering with my beach time ! 
I did a big sweep out of both tents, I’m going to do another one every few days. I noticed the treatments slowed leaf drop right away !
@durabloom let us know what you doing & how it works out
-good luck
Sounds like nitrogen toxicity, sorry tagged wrong person. If it is mold will (garrigan62) have you a good explanation