they like stop developing, and sit there for 2-3 weeks with almost no visible development, some of them got a very small true leave, that doesn't grow. After that they start to get dry from the border of the leaves and finally just dry out.

Sounds like root damage from over-watering. Different mixes retain and drain water differently so requires adjustment by the grower.

Seedling roots are easily damaged, drowned, compressed, suffocated, etc. and over-watering is the most common cause.

There are other possible causes of course - like the mix you are using this year - very prone to compaction and high water retention.

Dave

"they like stop developing, and sit there for 2-3 weeks with almost no visible development, some of them got a very small true leave, that doesn't grow. After that they start to get dry from the border of the leaves and finally just dry out."

I had an aphid infestation last year and it did just that. The sprouts with cotyledon leaves just sat there for weeks, kind of deformed looking, with very small leaves. I finally examined the little month old sprouts, they had dozens of small aphids tapping the stem for nutrients. If not, Perhaps damp off?

Thank you both! I think the word "suffocated" will be exact word! I remembered what i did different last two years. I red in Vegetable garden guide online that cabbages like very firm soil. So I thought it is applicable to the seedlings as well. So I compacted the mix in the pot a little, before I planted the seeds. And I didn't do this first year, as I didn't know the fact the cabbage likes firm soil). So sometimes, no knowledge is better, when you follow the common sense. Fortunately, the spring is so slow this year, I can plant them again and will not be too late to plant them out when they ready.