Dehydrated or something else?

I think you're being a little to quick and aggressive for your first grow. After you have 5-6 nodes, top the plant. Wait for it to recover and grow new branches. Add a scrog net Continue to train Defoliate under the net

Thats way too much water.. only water when they are completely dry.. maybe 1 or 2 times a week 500ml

Yes, stressed from growing at 24/0. Go to 18/6, ALL cannabis plants NEED "sleep" for a correctly functioning metabolism. A plant with an incorrectly functioning metabolism will never grow to its full potential or at its peak of health. Water when necessary, not to a schedule, unless it is coco or hydro. You will also need to use a "grow" type fertilizer.......power roots and pure zym are supplements, not true fertilizers. They will also need transplanting soon, 5l pots are too small.

Overwatered i think, even the soil on top looks kinda wet. Just for example, i had 11L Pots on my last run and used around 2.2L every 4-6 days. So i think you use a little bit too much water with 1.5L, rather go down to 1.1L and then really wait until the soil is dry enough before you give them something again. Just because the top is dry doesn't mean everything is. The best thing you can do pick up a dry pot which needs water, remember how light it is, then give it water and see how heavy it got. After a few days you lift it up again, if it's as light as last time it gets water again, if not then not. Also water them slowly. Like 400ml slowly, 5 minutes later the next 400ml slowly, then the rest. Like that you will make sure the soil will soak it up instead of just letting the water through.