Only mix what you can use immediately. As far as stages of growth, meh. More to do with size of the plant and not being wasteful with nutes. Figure out what your plants need to get 10% runoff from dry. Mx that much, water it in, let them dry out, repeat. If those are 3 gal smartpots, youll be at about 1 litre per plant. 1 tsp=5 ml, i round down to 1 ml for a qt. For a hlf gal, i round up to 3 ml.