Proč se to děje? Nedostatek draslíku?

Hi 👋🏻 ### What you’re seeing here Those fan leaves with **yellowing between the veins while the veins stay darker** + the **purpling/bronzing tint** are classic **late-flower magnesium fade**, often paired with normal senescence. This is **not a disease** and not a “you messed up” issue. --- ### Breakdown (plain English) #### 1. **Magnesium depletion (very common late flower)** * Interveinal yellowing ✔️ * Starts on older fan leaves ✔️ * Shows up when buds are swelling hard ✔️ In flower, Mg demand spikes while uptake drops — especially in coco or under strong LEDs. #### 2. **Genetic + cold color expression** * Purples / dark reds creeping in * No necrotic spots or crispy margins yet This usually shows when: * Temps dip at lights off * Nitrogen is fading * Plant is nearing the finish line Totally normal. #### 3. **End-of-life nutrient reallocation** The plant is **cannibalizing leaves to feed flowers**. That’s exactly what you want at this stage. --- ### What this is *not* 🚫 Not calcium deficiency 🚫 Not phosphorus deficiency 🚫 Not overwatering 🚫 Not lockout 🚫 Not bud rot or mold 🚫 Not something that needs “fixing” urgently --- ### What I would (and wouldn’t) do now **DO:** * Keep environment steady * Maintain airflow * Let leaves fade naturally * Focus on trichomes, not leaf color **OPTIONAL (only if 2 weeks from harvest):** * Very light Cal-Mag (¼–½ strength) **one or two waterings max** **DO NOT:** * Chase deficiencies aggressively * Jack up EC * Foliar spray in flower * Panic 😄 --- ### Big picture This plant is **finishing strong**. The buds look healthy, frosty, and on schedule. Leaf fade like this is **normal and expected** near the end. If you want, next we can: * Dial harvest timing by trichomes * Talk whether to let it fade harder or hold green a bit longer * Compare this fade vs a true deficiency so you can spot the difference instantly next run You’re doing better than you think 🌱💪

Salam! 👋 I see you are asking about Potassium (Draslík). 🍌 Before you add more nutrients, let's use some "Modern Engineering" logic to be sure, because Nutrient Burn often looks exactly like Potassium deficiency! ⚠️ The 3-Point Check: 🛠️ Location: Does it start at the bottom (old leaves)? If yes, it could be Potassium deficiency. If it is at the top (new leaves), it is likely Light Burn or heat stress. ☀️ The Tips: If only the very tips are brown/burnt (like painted fingernails), that is usually Nutrient Burn (too much food). 🛑 pH Check: If your pH is too low (under 6.0 in soil), the plant cannot "eat" the Potassium even if it is there. This is a "lockout." 🔒 Check your runoff pH first! If the pH is good and the problem is on the bottom leaves, then you can add more Bloom food. Happy Growing! 💚

I second the overfeeding / lockout answers. Seeing how it progressed would help too. leaf symptoms are not discrete.

Myslím, že je přehnojená, špičky horních listů jsou drobivé a trochu zbarvené. Tyto skvrny mohou být jen mírný nedostatek vápníku, je tu také nějaký nedostatek fosforu, ale v této fázi bych si tím moc nelámal hlavu. Zkus trochu snížit hnojení a EC. Jaké hodnoty používáš při zálivce? I think it’s overfertilized, the tips of the top leaves are crumbly and a bit discolored. These spots might just be a slight calcium deficiency, and there is some phosphorus deficiency as well, but I wouldn’t worry too much about that this late. Try lowering the fertilizer a bit and the EC. What values are you using

Yes, P-K deficiency. EC of the media is to low at this stage of the cycle. It should be somewhere around 2.4 Increase the amount of P-K and switch from Cal/Mag to Mag/Sulfur.

Burning from long term over feeding and a build up of nutrient salts in the substrate. It is not a deficiency. Deficiencies show through the entire plant, not just in random leaves.

​🌟 What You’re Doing Right ​First off, props to you for monitoring your runoff. Knowing your pH (6.3) and EC (1.0) is the absolute foundation of professional growing. You’re using an 11L pot with Light Mix, which is a smart choice for maintaining control, and your current substrate pH is sitting right in the "sweet spot" for nutrient uptake. ​🧐 The Diagnosis: Why the Brown Spots? ​While brown spots can often look like a Potassium (K) deficiency, given your history of high EC, we are likely looking at the aftermath of a nutrient lockout or a Calcium/Magnesium shift. ​Nutrient Lockout Recovery: When your EC was high previously, salts accumulated in the soil. This "locked" the roots, preventing them from absorbing specific elements. Brown, crispy spots on the upper leaves often appear when the plant is transpiring rapidly under lights but cannot move immobile elements like Calcium (Ca) to the top fast enough. ​Exhausted Light Mix: Biobizz Light Mix is excellent, but after 9 weeks, it is completely depleted. If your last flush brought the runoff EC down to 1.0, the soil is now very "clean," but potentially too lean for a plant that still has weeks of fattening up to do. ​Potassium vs. Calcium: Potassium deficiency usually manifests as "burnt" leaf edges (looking like a cigarette burn around the perimeter). These localized brown spots on the upper canopy are the classic signature of past pH fluctuations or a Calcium deficiency triggered by the previous salt buildup. ​🛠️ How to Fix and Manage It ​Stabilize and Feed: Since you’ve flushed the excess salts and your runoff EC is at 1.0, it’s time to reintroduce nutrients—but gently. Resume your flowering nutrients at a lower dose, and critically, add a CalMag supplement. In week 9, the plant’s demand for Calcium under intense lighting is at its peak. ​Check Light Distance: If the spots are strictly on the topmost leaves, check your light height. Heat stress accelerates nutrient evaporation in the leaves, making "calcium spots" appear much faster. ​Potassium Boost: If the leaf edges start to yellow or curl upward, slightly increase your Bio-Bloom or Top-Max, but stay at about 75% of the recommended dose until the plant stabilizes. ​🛡️ How to Avoid This in the Future ​The 20% Rule: Aim for about 10–20% runoff every time you water. This ensures that old salts are pushed out before they can accumulate and spike your EC. ​Enzymes are Key: Use an enzyme product (like Acti-Vera or similar). Enzymes break down dead root material and salt deposits, keeping the "rhizosphere" (root zone) healthy and breathable. ​Don't Starve the Light Mix: Remember that Light Mix is a medium, not a food source. You have to be consistent with your feeding schedule starting from week 3, as the soil provides very little buffer.