New grower with questions/problems. (Pics included)

What's up every1 Few quick questions:

I have 2 clones just about the same size



When should I begin adding nutrients to my clones? Can I begin now?




Also can anyone tell me what the problem can be with the leaves that are light on the edges and the black spot? I had this clone directly under my 400watt HPS, (fan running also) for 1 light cycle of 16 hours and this turned up. The PH of the soil is 7 and the light is above head well over 20 inches. Is this a nutrients problem or should I not have the plants directly under the light?Any help and tips is appreciated.

P.S also, can anyone give me a link to a thread or site that shows hydroponic grow methods without soil? thanks.

im thinking those black parts are because of the soil, i had a soil like that then moved to more pure dirt (without all the rocks and crap) and my new clones stayed flush green all through out their lives