Just my personal experience:

I've got a super lemon haze going, and from seedling I tossed her straight into a 3 gallon pot, it's been 2 weeks and the 2nd node is barely even coming through - This is indeed because the seedlings roots are expanding - as soon as I see verticle growth, it will be very rapid, and it will only be about a week before I toss her into flower after she starts coming up hard - I'm not worried about the lack of growth because the seedling is still very healthy.

Don't use your food AT ALL until you start seeing vertical movement, the roots are like fine hairs, and if you suffocate them with food, they won't preform the way they're intended to form
low_rdr Reviewed by low_rdr on . it wont grow my seedling popped up,about two inches high and the bottom single leaves yellowed like hell(don't know what it was,i think it was in the blazing sun too long, but they curled up and fucked out anyway)the top leaves look good as. anyway its been about three weeks now and the plant doesn't seem to grow any bigger.i transplanted it a week ago just in case it was the seedling pot being to small or something wrong with the soil.iv tried different things,more water,less water,less or no nutrients , Rating: 5