I saw this post and had to create an account and chime in. From my understanding, I've been growing hydro for some time now, that no matter what your concentrate will always be 5-5-5. 5% Nitrogen, 5% Phosphorus, and 5% Potassium, changing the nutrient concentration comes with how much you dilute it. Lets say a liquid fert says to use 10mL for 1gal, even if you put in 5mL you would still be adding a concentrate of 5-5-5, but if you used 5mL for one gallon the nutrients would be at half strength. A way to test your nutrient concentration is by getting a ppm/TDS/EC meter, and I highly recommend one to monitor the exact levels your giving your plants.
As for how much to feed your plants it depends on how big they are
~100ppm for sprouts
~early veg 300-400ppm (usually 1/4 of what bottle says)
~late veg 450-700ppm
~early bloom 750-950ppm
-full bloom 1000-1200ppm
Depending on what you have for a nutrient they may have a nutrient calculator on their website. The use and ease with a ppm meter is really nice, being able to know how much your actually feeding your plant, esp when you start using 2, 3, or more different bottles.
Though for soil I second Proud Marine Dad, mix a killer soil and I usually only end up adding molasses