The reason: early-transplanting in the ground.
Cauliflower is not so hardy as cabbage. Enough for the frosts to -1 degree, so that the growing point was killed.
Reason: irregular watering.
Even short-term drying of the soil in the seedling period in the future will have a negative impact on the education of the head.
The reason: the growing of seedlings in shallow pots.
Head size depends on the size of the leaves: the bigger they are, the more can be head. So grow seedlings cauliflower into larger pots than white (8x8 or 10x10 cm).
Reason: lack of supply.
Cauliflower has very high power requirements. As soon as the planted seedlings take root and begin to grow, it is necessary to feed the solution of mullein or bird droppings with the addition of superphosphate (3 g per 1 liter of water). A second foliar application should be held in 2 weeks. Can be used again mullein, dilute it 1:5 with the addition of superphosphate 6g per 1 liter of water and potassium sulfate 2H spoons. If necessary, you can do a third feeding.
The reason: a lack of soil trace elements such as boron, copper, manganese, zinc, molybdenum.
Spend fertilizing with micronutrients. In the absence of such use, kiln, wood ash - 1-2 tablespoons under the plant.