Blätter Farbe und Verbrannt

too many nutrients too often watered let the soil get visibly dry before feeding, doesnt matter how long it takes. use exactly what it says on the bottle for nutrients water until you see runoff then stop

Magnesium deficiency either pots were too often too wet for too long and changed pots ph either overfeed of nitrogen blocks it or young rapid grow under intense light need calmag as extra supplement and shows you signs https://www.growbarato.net/blog/en/deficiencies-due-to-excess-nutrients/ Happy Growing !!!

I would go with a deficiency. I would say iron or nitrogen. Where did the yellowing start? On the bottom leave or the top? Here is a nice resource for diagnosing problems https://www.ilovegrowingmarijuana.com/growing/identify-marijuana-plant-problems/