Depending on how much the supplements bring up the ppm depends on how much base you can run, assuming you have a goal for your total ppm final number. Since you're running seedlings maybe only supplements and micros to start and what ever additives you have that will help your rooting babies get a good start. You won't need much of anything for the first couple of weeks and gradually up the nutes until you have them in full veg. Supplements, Nutrients, Additives and then pH, or S.N.A.P. Best, Irie.