Adlerkrallen?

Thank you for the much better pictures! Yes, too much nitrogen will cause these symptoms. Try giving just plain water for the next 3-4 irrigations and then resume at half the strength of whichever nutrients you are using. Although you are feeding relatively little, the soil will contain some nutrients already, so giving extra nutrients can be a little too much at this early stage of their lives. Also, giving plain water 2-3 times and then one feeding is generally enough at this young age, as feeding each and every watering can cause nutrients to build up to toxic levels quite quickly in pure soil. Your plant will not suffer anything, growth or nutritionally, when feeding only every second or third watering. At this age/size, your plants require very little by way of feeding and half strength is plenty powerful enough. Once they have 10-12 nodes, feed either more often or then go to full strength every third/fourth irrigation. Remember too, it is very easy to correct a slight under feeding than it is to rescue a burnt, over fed plant. Fortunately you acted quickly on this issue and did not continue until it was too late! Viel gluck! Hope this helps,.... Organoman.

Also die Pflanzen mit den Beschwerden spülen? Die anderen können ganz normal weiter wachsen?