Stickstoffüberschuss?

Yes, showing signs of nitrogen toxicity......over feeding. In soil growing, a schedule of plain water/plain water/fertilizer/plain water/plain water/fertilizer......works well. Never fertilize every time you irrigate, the plant needs to use what is already there, before more nutrients are added. Also, make sure you are getting 10-20% run off (water coming out of the bottom of the pot) each time you irrigate, this helps to prevent nutrient salts from building up in the substrate and causing problems in the root zone and is essential for plant health.