Stonerdanswered grow question 4 years ago Once they fully develop their first set of leaves (when the second set starts to pop out and grow)!
When you do please keep your plants about 50-60cm from the lamp and make sure they are not getting too much heat off it!
To check if it's too hot for your plants put your hand over the top of the plant with the back of your hand facing the lamp, if it's hot for you then it's hot for the plant!
Hope this helps! Good luck and happy growing :)