Blattprobleme bei Pflanze (Wahrscheinlicher Kalziummangel?)

luckily you are near the end, so not much matters and they'll finish fine. the progression helps diagnose. looking at severe issues after the fact is less helpful. ph-lockout, nute lockout, simply the wrong concentration of a particular nute fed... symptoms are not discrete. Something impacting K or physically low K available would be my guess. But again, at this stage, i wouldn't react too strongly.. maybe try increasing K slightly without impacting levels of other nutes provided and see if the damage slows... if it continues or gets worse, less likely realted to k. not all plants are the same, but "better" formulas will work on a wider variety of plants.