I’ve not used promix nor botanicare before but they definitely need food. You should treat it as hydro or coco so PH 5.5-6.2. I usually start feeding after the first set of real leaves come in which you are already past.
is the 630-watt light, 630 watts from the wall? I run around 15w per sqft in veg and 25ish in flower. You really don’t need much for seedlings, just enough so they don’t stretch a bunch.