Ab wann düngen?

If you stick to BioBizz schedule (there is one for AllMix and one for LightMix): https://pevgrow.com/blog/wp-content/uploads/2020/12/nutrient-schedule.jpg You will have 0 problems and have a really safe grow

Seedling that age feed @ 125-150 ppm. Cheers!

You're at about the right time in an autoflower's life to start nutes - but don't start with a full dose of anything! Start out slowly (1/4-1/2 the recommended dose). From the look of your grow, they'll definitely benefit but need to be given nutes slowly! Good luck!

When to start feeding depends on what soil you're using. Biobizz or any other organic nutrients are long time release. Means the plants absorbs what it need from the soil along time rather than instantly on every watering. If you're using biobizz all mix for example you only need to give them nutes after the 4th week. Just boosters before that like aminoacids or microbes. If you're using light mix you can start feeding on the second week. Before that is really not needed but won't hurt either. I advise you to get beneficial microbes like the product from AGROBACTERIAS - Bactohemp and Bactobloom. Real good with organic grows.

Hey Buddy this is the right time to start feeding with a low dose , i work with biobizz for years now, but start with 0,5 ml/l and if you have another products of biobizz then use Alga Mic as spray for the leaves 1-2 a week , you will see big changes. Good luck with your grow 👍

It's better to wait another 2 weeks, seedlings don't need much nutrientes.