First time grower, 2x 150 watt HPS vapor tights

I just recently got some free seeds that are like 8 years old, one is Black Dog( if anyone has any info on these strains please let me know!), from Willy Jack, and Mighty might/Skunk #1. Most all the other ones are from this anonymous vaccum sealed bag with like 20 seeds. These pics are 7 days in.

the grow medium is a 50/50 mix of pearlite and MG regular potting soil.
I dont have any other nutrients yet, any suggestions would be helpfull. I heard that MG already has alot of fertilizer in it already.

I am growing in the closet. witch is a convenient place to hang lights.
The space is 2x6, and 5ish feet tall.

i know its like against the rules or somethin to write in journels, but you're gonna kill your plants with em mirrors in there... mirrors don't reflect light, they concentrate it

this is day 8 from sprout.
i am using superthrive now and it seems to be helping, first timer though.
18/6 light cycle.