Nährstoff überdosis?

feed every second watering

Burning from feeding too much. Also pots that are waaaaaaay too small = nutrient salt build up = burning = yellow/brown patches. Transplant and feed less = problems solved. Bitte schon.

Hey bro. I know what this is. Well, it's a mix of 3 things really. Cal mag and sulphur mixed in. I had the very same thing much worse on week 3. It's like paint chips missing off your plant right. 2nd last pic growdiaries.com/diaries/141638-grow-journal-by-gottagrowsometime/week/775784 My fix is in it. But basically some calmag and if you have any Epsom salt would be a great source of Mag sulphate. Good luck bro.

It could be the beginning sign of a deficiency as it appears to be affecting multiple plants, I would double check the PH of whatever nutrition you're adding into the soil. Additionally, you could check for insects on the underside of the leaves and along the stems. If there are no insects, and your PH devices is calibrated correctly, it could be a buildup of salts in the soil or some type of fungus. Apart from the cloth pot do you have drainage holes at the bottom of your buckets and containers? You should have some form of runoff to allow the salts to leech from the soil, if not they will simply accumulate over time and cause nutrient deficiencies and or PH imbalances. Hope this helps.

Honestly, I have no idea - but I wouldn't worry about it... the newer leaves look just fine and often those first leaves do weird things either in terms of color or shape. Carry on... looks good! Good luck!