Brown "splotches" on lower leaves

I am growing indoors. I set my relative humidity to 60%. The PPF is about 650. I am seeing brown splotches on lower leaves:

I am hoping for insight into what is causing this and what I should do to fix it. I think it might possibly be a fungi from the soil?

Thank you.

Are you growing in a coco based medium? It looks like possibly a calcium deficiency which can be common.

Are you watering with tap water? If not, or even if so you might want to supplement with some cal mag.

@solarslurpie what are your temps? What cultivar/strain are you growing? Is it an auto or photo? Along with the brown spots I can see that your leaves are starting to yellow from the outside in as well.

Usually when you see a combination of nitrogen deficiency along with calcium and magnesium deficiencies it’s either a vpd issue, over watering, potassium lockout, or under feeding. I don’t really see any of the burning yet that comes with vpd issues or lockout unless this is just early stage. So it’s likely either over watering or under feeding.

I would look into the other issues first before just feeding more and possibly making the issue worse. First check soil pH to make sure it isn’t potassium lockout. If it’s potassium lockout your soil pH at the root zone will be high. Usually over 7.

If your pH is good test for vpd issues. If your temps are 75f or more try splitting up your feed into two separate feedings. So if you feed once a week split your weekly feeding in half and feed it a half dose twice a week. This will solve the issue if it is vpd related.

To make sure it isn’t over watering water less frequently. You can saturate the entire pot if you want during a watering but wait to water again until the pot is almost completely dry. Cycling wet to dry is the best way to water.

If changing the feed schedule and cycling wet to dry doesn’t work you will need to increase your feed. Up your grow nutes and if your grow nutes don’t have calcium, magnesium, or other micros add some calmag and micro boosters.

Hope this helps man. Happy growing. :call_me_hand::metal::v:

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@solarslurpie also, just a quick way to test if it is mold is to try to rub it off. If it leaves a rust colored or brown/gray residue on your fingers it’s mold.

You can also check it with a scope to make 100% certain if it doesn’t leave a residue. You’ll need 60-100x magnification at least. Look at the spots and if you see fuzzy cratered spore heads on fuzzy stalks it’s mold.

By the look of it though I’m pretty certain it is a calmag issue because of the purple stems as well.

Also, when you correct a micro nutrient issue or immobile nutrient issue watch the new growth to make sure it is healthy. The old growth will keep the spots and scars but they won’t get any worse if corrected properly. New growth should come in looking green and healthy.