Nutrient deficiency or overdose?

Hey dimax, my best guess is your plant's symptoms—burnt tips, thin new growth, and yellowing leaves and or veins—point towards a mix of nutrient excess and deficiencies. The key issue seems to be an excess of potassium, which might be locking out magnesium, contributing to these symptoms. To tackle this, ease up on potassium-rich feeds, consider flushing the soil to remove excess nutrients, and ensure a balanced nutrient regimen moving forward. Keep monitoring and adjust as needed. At a pH of 6.8, you're within a range that's generally conducive for nutrient uptake in soil-grown cannabis plants, including magnesium. However, magnesium uptake can start to become less efficient as pH approaches the higher end of the optimal range (5.5-6.5 for soil). While 6.8 isn't far off, if your plant is showing signs of magnesium deficiency, you might want to slightly lower the pH to ensure better magnesium availability. Consider lowering the pH of your water/nutrient solution slightly, aiming for a range of 6.0 to 6.5, which is more ideal for magnesium uptake. Cheers, D.