wats the ph of that soil? also, have u fed any nutes yet? i wudnt worry about the yellowing on the new growth just yet, ive had that with a few of my 1st plants ive grown and it hasnt done any damage. as im on my 1st grow my advice is far from rok solid but id say nute burn, either from your soil being to strong which is unlikely if they were fine early on, or mayb u fed em? other than that it may b ph or sum other reason. experienced growers needed, cmon lets help this guy out