Brown spots

Hi. I think that you have a problem with PH or overflow. Use a high-quality, expensive device and calibrate yours with a buffer solution.

All Mix is very rich in nutrients, you should not have to feed for 3-4 weeks at least. Cannabis leaves arch downwards naturally, it is not a sign to fertilize them. Your plants are very, very dark green, indicating more than enough nitrogen. The yellow "spots" on the leaf tips are actually the first signs of burning from over feeding. I would suggest stopping all fertilizers for about 2 weeks and only give plain water in that time. Once you resume feeding, half strength should be a good (and logical) starting point. Remember.........it is very easy to fix a slighly under fed plant, but very, very hard to rescue a burned and damaged over fed plant!

Hey 👋 Looks like your tips start burning from overfeeding with nitrogen. Additional indication is also the very dark green color of your leaves. Me personal I would stop feeding her grow fertilizer (e.g. BioBizz Grow in my personal case, but depends on which fertilizer you use), and would water them with pure water & CalMag for at least one week. This should already help your plant to recover 👍 Hope i could help. Happy growing 👊🍀