Identifying deficiency - very new grower here!

Hi there!

Very new to growing. I recieved these plants 4 weeks ago and transferred them to larger pots and used a potting soil. They have since tripled in size and have been very healthy up until this point.

The last couple days these spots appeared and are getting worse. Any ideas on what deficiency this could be?

I have been using regular tap water and wondering if it has made the soil acidic?

Thank you for helping out a newb in advance!

Check the under side of the leaves with some magnification. Looks like a pest problem to me.

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Yup concur with @AAA. Looks like pest have moved in.

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Thank you for the quick reply! I have checked behind all the leaves and don’t see anything, do you have any idea regarding type of pest? Or got to rid them?

Thanks again!

Use magnification to look. If they cam from an indoor grow room, I would guess spider mites.

@Myfriendis410 suggests spraying with straight peroxide, wait 2 days and spray with Captain Jack’s dead bug. Repeat weekly.


Spider mites are very common. I grow indoors and am VERY careful about what plants I bring in the house. (I check the over carefully to avoid those %@$# spider mites).

Outdoors you can easily pick them up or other pest. A search in the forum for pest control should help as well as google and YouTube.

AAA gave solid advice. Best to know what you are dealing with so the cure is most effective.

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Thank you all for the advice!! Very appreciated!!!

@Reticence is a smart man! JK. As we both agree, it’s probably pests. When starting outdoors you will always have some pests, usually mother nature keeps a healthy balance, but when getting plants from another environment(indoors) there could be egg cases in a large proportion that have not been kept in check by all of the natural predators in a garden. Chances are once you get this break out under wraps, things will balance out. You will always lose something to the pests unless you are hyper vigilante.

In my neck of the woods, caterpillars the enemy. Spray with BT weekly to stop them

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Likely pests. Could be: PH too low, cal mag needed. I would strongly suggest a slurry test of the soil using a decent PH meter and while you’re at it make sure you have a good TDS meter as well. Tap water needs to stand for 24 hours before use and should be PH’d into nominal soil range for cannabis: 6.3 to 6.8. If you aren’t doing this now it will bite you later. There are also micronutrients like silica that can toughen the plant and make it easier to fight off pests.

Look at a couple of lower leaves on the undersides of them up against the stem. Go ahead and remove the leaves so you can really examine them. Mites, FYI, are almost too small to see naked eye. You need a loupe.

If you look at the picture you can see some mites (purple) nestled into the tricomes of an earlier grow I had. I never saw them: just the web, until I got a digital otoscope and could see them moving.


Also, @Reticence s smart, but not just because he agreed with me!


Thank you for all of the information! I for sure did not look at that magnification! These are my first plants ever, so I am a bit (very) uneducated!

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Been there! Sometimes it’s tough to put all of the information together. Of course; all of my lessons are hard ones haha.


Has it been rainy and warm where your growing? Looks like leaf septoria.


When you are just starting out it is hard to stay calm and just work the problems. We have all been there!
Typical issues I see often:

  1. Over and Under watering throughout the life cycle
  2. Seedling too far away from light source causing stretch
  3. Not checking pH of water (Causes lots of issues if high or low)
    3a Don’t have a ph meter!
  4. Calcium (Spots on leaves) and Magnesium (Purple stems) deficiencies
  5. Not sure about what lights, tents, fans etc to buy if indoors

It goes on and on, but I have never seen a person ask for help and not get a respectful answer on this forum. Best folks ever!!


It has been pretty rainy and warm here, how would I fix that? Would it spread to all the leaves?

I there are a few ways to treat it but I can’t say for sure the specifics . I know there are treatments from hydrogen peroxide to milk sprays . Put it in the search bar and you will see many recommendations for treatment. Good luck!

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Thank you for your advice!

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