Use your ppm meter. If you have a scale, weigh up the amounts before you add them, then measure ppm. Shoot for 1EC (500ppm on my scale) for small plants in veg. As the plants get bigger, increase to 650ppm, then get up to 750ppm at start of flower. This will give you headroom to add 100ppm or so of cal/mag or epsom salts, and/or another 100ppm to 150ppm of bloom booster in later flower. Be sure to get ample runoff, then measure runoff. If the runoff it too high, water more, and consider lowering the ppms a bit. If the runoff is too low you know the plant can take more food. It's very strain dependent, so you have to gauge the plant. Indicas will often want more food, and sativas less. Hybrids are sometimes tricky, especially when they look Indica in veg, and then Sativa in flower.
... Shoot for 1EC (500ppm on my scale) for small plants in veg. ... If the runoff it too high, water more, and consider lowering the ppms a bit. If the runoff is too low you know the plant can take more food..