[Growing West]

I’ve been mixing my own potting soil for starting in Steuwe Deepots for quite a few years. Now that I am using a grow tent instead of an arboretum, it’s not working as well. I’m looking at a medium of just coir pith and vermiculite (aragonite at bottom). What fertilizer regiment should I use after true leaves establish themself? I’ve looked at the “Total Biome Organic Indoor Plant Food” product, but haven’t made a purchase. If anyone has a proven regime for a non-fertilized substrate, please share, thanks!