You really want to let the plant do its own thing for the first 3 weeks, without fertilizer or hormone boosts. There is a fine balance between how fast it can grow and how much food it had stored in its cotyledons... accelerating growth beyond what the plant can keep up with from its own resources is actually how some herbicides work!
Boost your little seedlings with bright, blue-spectrum light and correct temps/humidity. These are about 76'F-82'F and 60% during the early stages.