Blue Dream keeps getting leaf spots

Trying to grow Blue Dream (fem) indoors in homemade super-soil. Long story short, I keep running into disease and pest issues. Most recently identified and seem to have successfully treated for thrips; the plants recovered except for a few yellowing, dying leaves, which I pruned after several days of new growth appearing on top. Now I am seeing brown spots on yellowing leaves, curled up brown tips on the new leaves, and I have no idea where to begin.
Some details: I do not see any bugs or leaf-miner trails. I always soak my pruning tools in Everclear before and after use. Always wash my hands and such when I need to handle the plants or check the soil for watering. I wait until the top inch of the soil is bone-dry before watering, it’s usually a little moist still deeper down (2 inches or so). I water using RO water from a Culligan tap in our kitchen, and I’ve tested PH, it’s always 7 on the dot. The grow closet is about 4 feet by 3 feet by 8 feet tall. I run a Mars Hydro TSW 2000 LED grow light, currently at 50% power, hung 18 inches above the tops of the plants. The room is ventilated by a Cloudline T4 inline fan which pulls air out of the room at the top; air flows into the room from a vent at the bottom of the closet door that is covered by a furnace air filter. I’ve mostly sealed off the rest of the air gaps around the door and within the room. The walls of the room are covered in mylar film. Humidity stays between 50-65% at all times, and temp stays between 71-84 F at all times. I use RO water in a cool mist humidifier with a humidistat to maintain humidity, and the light is enough to heat the room sufficiently. Ventilation and humidification are for the most part automated to stay in the range I listed. With all this, I have been expecting great results, but unfortunately, this is always what the plant ends up looking like:

Close-up of the leaves:

Any ideas? Can this be saved? What might I be doing wrong?

Some prior treatments I have tried:
For thrips, sprayed neem oil once, applied diatomaceous earth to the soil surface and around the base of the pots, then sprayed Pyrethrin a week later when I still found bugs. One week after that, all the bugs I found were dead (checked for movement under a scope, saw none.) A few days later, new growth started up again, and all looked well; I pruned off the dead and dying leaves with thrip damage, and a week later the plant looks like the pictures. No bugs appear under the scope. No idea what this is or what is causing it, but I need help!

Let me know if I can share any more helpful details or pictures, any help would be greatly appreciated!

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Hard to say without some run off numbers or a soil slurry test. Watering frequency could be a partial factor, soil likes a wet to dry cycle beyond an 1” below the top. PH is on the high end, 6.5 would be the sweet spot. The super soil could be super hot or depleted leaning towards depleted if all she’s had is water??

Hey thanks for the reply!
I’d be happy to run any tests I can afford the equipment for and share the numbers. Any product/equipment/method recommendations to accomplish this would be neat, I love getting scientific. All I have currently is a digital pH probe.

On watering: I would LOVE some experienced, expert help on this, i.e. how should the soil feel when it needs water, how deep should it feel that way, how much water should I give it when it does need water, should I wait until the plant looks a certain way before watering, etc.? For reference, I grow garden vegetables pretty successfully, including tomatoes outdoors, and I have tried my hardest to get the watering thing right, but to no avail it seems. Having never grown cannabis before now, I need some specifics! My methods as described come from various places on the web, including the guides here. Seems to be a lot of conflicting info out there.

Thoughts?

Lift your pot when dry, then compare with when watered. This will give u an idea. Cannibis has to be dry, then watered.
Your ph is too high. For soil it’s 6.5. ish
Please fill this support ticket out so we know.

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Strain: ilgm Blue Dream Feminized
Method: soil (can provide recipe, used all organic ingredients)
Vessels: Pots, black plastic, 1 trade gallon
Water pH: 7.0
Runoff pH: not sure, will test when I water next!
Nutrient solution: not used
Indoor
Lighting: Mars Hydro TSW 2000 LED
Temp (day): 79-82 F (night): 72-74 F
Humidity (day): 55-65% (night): 65-66%
Ventilation (exhaust): Cloudline T4 4 inch inline fan
Ventilation (intake): passive air flow through 16x25 inch duct fitted with paper air filter
Humidifier: yes
AC, De-humidifier, Co2: No to all these

No expert here but I actually used a bathroom scale to weigh my plants a for a while to get the relationship to how they feel. Water weighs about 8 pounds a gallon.

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@beachglass recommended what a lot of growers do. They get a feel for the dry and weight weight of the pot. The larger the pot… typically leads to a longer wait on the dry cycle. Watering or feeding to approximately 20% of the amount your putting in should run out the bottom. This is called the run off and it serves a few purposes like rinsing the left over salts from the previous feeding preventing issues in the root zone that could lock out nutrient uptake. Also allows you to test the run off for PPMs and PH. This will let you know if their eating and how much to feed the next round. Soil generally likes feed, water , feed, water cycle :love_you_gesture:

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I’ll get a pot the same size and fill it with dry soil and weigh it, that seems like good advice.
I didn’t want to wait to water before getting some more numbers up here, so I got a slurry sample from the pot today, followed the directions on the probe, and the mixture pH reads 7.0 as well.
I’ll try to get a ppm probe for fertility today, will report back results when I get them. Saving the slurry sample from today in a sealed glass jar for that purpose.

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Welcome to the community :blush: what are you using to check your ph? :blush::v:

Thanks!
I have a Rapitest brand digital soil pH meter from luster leaf, bought at the local nursery.

Could this be a symptom of being root-bound? The plant is 9 weeks along, wonder if a 1 trade gallon pot is too small at this point? Does cannabis adapt to the size of pot it’s in?
I ask because today was the day I had planned to transplant into a 5 gallon bucket, and when I pulled the pot free of the root ball, this is what I found:

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She’s definitely ready for a transplant, personally I wouldn’t go 9 weeks on the next one :love_you_gesture:

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Got a better pH meter, now using a GroStar GS1. Our RO water from the culligan tests out at 8.2 pH with the new meter after a fresh calibration.
I didn’t see any signs of root rot, all the roots looked like healthy plant roots, so I’m hoping she will tolerate the watering in in her new home. Weighed the dry bucket and marked the weight so I know when she needs water next!
Transplanted into her new home and watered her in until roughly 20% runoff (same soil mix, same RO water from the tap).
Tested the runoff and got 6.9 pH.

Really hope it was just lack of room to grow after seeing the root ball. How do my numbers look? I have to wait a week for a TDS meter, the local hydroponics shop was out of stock, so those numbers will have to wait.

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Great job and those roots will spread out now. The PH is at the high range with 6.5 being the sweet spot :love_you_gesture:

Thanks! She still looks pretty sad this morning, but I still see green leaves, so I have hope…
Should I amend the soil or the water to correct for pH? It seems the soil brought the water pH down by a lot if I remember how pH works (college chemistry was… challenging… for me, to say the least.)

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You’re close enough in range to lower the PH of your water or nutrient mixture to correct the higher PH :love_you_gesture: