Thanks might wait till she's about 7-8 inches tallAt all times, but if you want to wait like I do.
I wait until I can start smelling my vegging plants then I ad my ductwork and extractor fan, I always have and osculating fan running in the room blowing the plants. Be mindful, you want to move the fan or alternate the plants around they could get wind burn.
When is the best time to use inline intake fan and inline extractor fan for ventilation pics of my plants she had no fans on in there just a cfl 300w dual spec