Was kann ich machen?

La floración va bien lo que puede ser es un exagero de los nutrientes , pero los pistillos se veen bien, usted está ocupando los nutrientes con su respectiva tabla ?

IF it is Ph, you should flush with Ph-balanced water to reestablish the correct values. But this is a big IF without info (e.g. a diary).

Was kann ich dagegen machen? Mit destillierten Wasser gießen oder erst spülen

Not a lot of information, but it seems some nutrient block. Did you check your Ph? Last run I experienced Ph issues, with consequent nutrient block, which look like in your pictures. With wrong Ph the plant is not able to get nutrients, and try to absorb them from the reserves in the leaves, which turn yellow, brown and then die. If you didn't I suggest to buy a Ph pen and make sure to fit the range (I go usually around 6-6.3, which is also good for Calcium)

Die gelben Blätter stören mich

Would you give us some indication of what concerns you?