depends on how hot the soil is. Some options don't need to be fertilized for 6-8 weeks. if not familiar with the products it's a matter of trial and error. too many variables to give specific instructions. observe plant and when you see hints of deficiency start with a low-dose. take not of the timing and next cycle start fertilizing slightly sooner to avoid any deficiency.
The plant will suck down and shed the cotys at any hint of low nute level in the soil, but doesn't mean you need full strength immediately. Depending on how strong instructed dose is you probably want to start at 1/4 - 1/2 strength. It's always easier to amp up and much more difficult to correct an overfeed. trust what you see.
should really start with smaller pots. this will make watering/fertigating even more difficult. Root development will be less than optimal starting in a huge pot relative to plant size, too.
molasses feed microbes. 1tbsp/gallon is something i recall reading.