What about timing?
Many of those plants are difficult to grow... requiring precise timing of seed planting and constant provision of moisture, nutrients, and even potentially shading.
In my area, broccoli seems to produce small heads... Cauliflower? I wouldn't even attempt! To get those white florets, I think they have to tie the leaves over them...
Carrots can be grown here... If we plant them in the sand!
According to the vidalia onion people, the sand allows the sulfur to be washed down through the soil, permitting us to grow a sweeter crop.
I can't tell that you are doing anything wrong... Except trying to grow specialty crops...
I usually try to avoid planting the difficult plants until such time that I'm ready to be challenged.
Again, It could be a simple matter of starting the seed earlier.
And... The need for a sandy soil structure in the case of carrots.
