Grow Medium and correct fert. strenght

[foxysox]

If you're using a soil-less mix, when do you begin vegetative feeding?

Same as any other mix... it depends on the plant...
Start giving your sprouts ferts when they have grown 4 sets of ADULT leaves (not counting the cotyledons!).
Use a veg fert at 1/4 strength for the first feeding, and work up to full strength.
This is also about the time when you will be doing your first transplant, if you have got things worked out right...
seedling starting soil is different from what you want for veg...
stinky's soil mix is fantastic for veg, but not appropriate for young seedlings, as it is too 'hot' and may burn them.
So you're going to be giving your young veggers ferts AND putting them into 'grown-up' soil at the same time, so use superthrive too for the watering right after transplant.