seedling question +rep

hello riu i have a couple of seedlings that are on there second pair of true leaves my question is when can i put them in the dwc system and when should i add the nutes?? im usein gh lucas formula. what strength also?? thanx

They need a good root system and u have to keep the nutes really low EC 0.4-0.6 until they can take 0.8, then they should be strong enough. 2 sets of leaves isn't much.