Nährstoffmangel?

Magnesium deficiency. Add some cal/mag to your line up or increase the dosage if already using one. She will also be getting hungry for P/K at this stage too. I can't see any real signs of nitrogen toxicity, the few yellow tips could be the first signs of being hungry for phosphorous. I would expect to see all leaf tips curling under/clawing if it were a nitrogen over feeding issue.

Kein Mangel sondern zuviel Stickstoff durch die Jauche. Das krallen der Blatter und die verbrannten Spitzen sind die Anzeichen.

It is mimicking some magnesium issues, now if it does not have it or if its unavailable is the question. I agree their is to much N and in your diary it looks like you might need to work on your watering practices as the one plant looks overwatered and this will cause a lot of root issues that look like deficiencies. PH is also an issue but Its not showing to many signs of an off PH. No idea what green power or Brennnesseljauche is, maybe post some web links of the products or nutrition labels. See if they have any Mg in them, if not add in some via epsom salts. Dial back the N a bit and let it go for a bit and see how it reacts. Good Luck!

Its not missing sign, its too much nitrogen sign. Nail polish i think its called, almost verge of overfeeding which leads to toxicity and lockouts. But i see lack of magnesium, that tigery striping in colour, epsom salt or calmag in small doses would be very wise.