ill tell u why they are growing slow.... its ur PH , organic will have a constant acidic value. i just know by looking at them the the ph isnt right. u really need to get sum way of testing the ph. get a ph meter from ur local hydro/ pet store they are not expensive but they are a MUST if you are going to grow. at the age of those seedling mate they should be alot bigger. what i suggest u do is this.... try getting a soil with a neutral ph (coco/coir is prefect for this) also get clay pepples/hydron and mix ur soil to a 50/50 mix. transplant those seedlings into the new mix. like i said earlier u really a ph meter and if ur feeding in coco keep your ph of ur feed between 6.0 and 6.5 ph. i also suggest u go the little extra and buy nutes intended for weed. general hydroponics flora series is a 3 part feed ( grow/mirco/bloom) that will give great results for new and old growers alike. its simple to use and u can be sure ur babies are getting what they need. so u have another place to flower these plants? because that box will not be big enuff.

so basically what i am saying is ur PH is the problem at the minute , at a guess id say your soil too acidic. change the soil , get a ph meter and good nutes and ull see a difference in a day .

i hope this helps