Nute issues... Any ideas?

PK deficiency or lockout due to Ca

I would add (to my last response) that if you did exceed the recommended fertilizer instructions, you may have a build up of salts and watering with plain water to flush them out will help.

It looks to me like week 9 you may have exceeded the instructions for the fertilizer you are using (not familiar with your nutrients, but the online instructions seem to suggest a smaller application spread over four weeks). Before 9 weeks I don't see the spots, suggesting that may have been the cause. When it comes to diagnosising plant stress I always consider the last variable that changed. But, it looks like you'll still have a great harvest! In the future I would recommend you consider a steady nutrient delivery plan. Plants like a certain level (in PPM) of nutrients consistently, significantly above or below this level will cause stress. Almost all fertilizers have instructions to keep you in the safe zone. And I wouldn't recommend combining different fertilizers unless instructed to so on the packaging or you understand the nutrient levels you are targeting. Here's an article from a gardener I really like that gives a little more food for thought on the subject: www.gardenmyths.com/best-fertilizer-indoor-plants For your fungus gnats I would suggest covering the surface of your soil in diatomaceous earth and using BTI, if you aren't already. Just my 2 cents. Hope this helps and happy growing!

Waaaay too much nitrogen and/or potassium and not enough calcium, which is the cause of the spots.

Does not look like iron. Iron affects the new growth. This looks like Calcium spotting to me. https://420life.com/wp-content/uploads/2021/10/Marijuana-Leaf-Deficiency-Chart-scaled.jpg It does look to be getting a bit to much N as the plants look extra lush.

doesn't look like Fe deficiency. You should google image search a 'marijuana leaf symptom chart' instead of guessing or relying on others who also don't use a leaf symptom chart, lol. Calcium is needed throughout its life. if you needed to add it early and stopped adding it, then that is likely the cause and the symptoms look right, too. Visible symptoms are not discrete. You need more infor to ensure you react properly to what you see. it's not Mg related because that would come with interveinal chlorosis and spots, not just spots alone. pH? this isn't really a question you should ask. We cannot test the soil or the runoff. Simply get some pH strips or a probe and figure it out, lol... One thing here you shouldknow is that these readings are not entirely accurate or precise. So, you need to learn a baseline of what is 'normal' when the plant is healthy before assumign anything from the readings. there will be an offset between reality of the substrate and what runoff or a soil slurry says.

Hey Growmie, The plant is looking solid overall, but I do see what your talking about in the first photo, it looks like early magnesium deficiency or possible pH-related micronutrient lockout. The rust-colored specks and interveinal discoloration on the older leaves are classic early mag signs, and that slight crisping at the edges could mean potassium’s not flowing great either.If you’ve been using Cal-Mag regularly and still getting this, definitely check your pH—too high (above 6.5 in soil) can block mag and iron uptake, and too low (under 6.0) can mess with potassium. Also, double-check runoff EC just in case salts are building up and messing with uptake. Try this: Feed with Cal-Mag + full nutes, pH’d to around 6.3–6.5. If it continues to spread upward, consider a mild flush with pH’d water and follow with a balanced feed. Rest of the plant still looks happy, so you’re not in bad shape, just needs a slight course correction.

Hey! From what you're describing – yellow-brown spots on fan leaves, mostly older ones – it does sound like a possible early-stage calcium deficiency, especially if Cal-Mag has helped before. 💡 That said, if the issue keeps coming back even with Cal-Mag, I'd definitely take a closer look at: pH – if it's too high or too low, your plant might not absorb the calcium properly, even if it's present. ➤ Try to keep it around 5.8–6.2 in coco/hydro, or 6.2–6.5 in soil. 📏 Salt buildup / lockout – if you're feeding heavily, it might be worth flushing or doing a light feed to reset things. Did you measured EC? Since the rest of the plant looks healthy, you're clearly not far off. Sometimes older leaves just give up naturally too, especially late in flower – but if it’s spreading, definitely dial in pH and monitor runoff. Good luck! Your instincts seem on point 👌🌿✨