Lookin at ur pics, you might want to flower soon. How much more headroom do you have in your box? That plant could grow as much as double or more in height once flowering is triggered. Just thought it was worth mentioning.

You shouldn't even NEED soil at all to germinate. All that is required for germination of cannabis seeds is moisture and relatively warm temperature (above 50F or so). I have done them in paper towels and a ziploc before and had 100%. Now I typically soak for 24 hrs in a test tube (until the outer shell cracks open), then plant directly in soil with no nutes. About 2 days or so, and a tiny little plant pops out.

Going right into the MG soil may be a little stressful since there is an abundance of nutrients and a seedling doesn't need any nutes for the first few weeks (typically).

Do a little research on Foxfarm use on the forums. I believe you must use Big Bloom in conjunction with Tiger Bloom to get good results. Something about BB being the catalyst for the mix. Not sure exactly, but before you make the investment, check it out.