As soon as the roots of your recently sown seeds grow out of their plugs they are ready to be transplanted.
Young plants are not ready yet for a heavily furtilized type of soil. They can best be transplanted first to a pot filled with a”light mix”.
The fibre pots filled with a lightly fertilized soil are the perfect intermediate phase for the young plants. The fibre pots can be planted in it’s entirety in a bigger pot filled with a more heavily fertilised type of soil.
After a few days the roots will grow through the walls of the fibre pots. At this time they will have developed enough and the plant is ready for more nutrition.
The fibre of the pots will eventualy perish in the soil.