Personally I like to start seedlings in something inert like Rapid Rooters, Coco Coir or Rock Wool its easy to burn the little ones up if the media has too much N. I usually grow in Hydro but I did start some seeds in Happy Frog and then moved them to Ocean Forest this summer and grew them outside. I didnt feed them anything until they started to flower and I think they broke records for the tallest plants with the lowest yield so maybe I am not the person to take advice from. I will say for sure go easy on the Silica until your done with LST unless you have a big roll of scotch tape and/or like cloning because it makes the branches hard and brittle.    .