i'd use 2 or 3 times the volume of the pot , and do it slowly, don't just dump it all in at once.
your plants won't grow more slowly till they eat all the nutes that come in your soil to begin with. foxfarms pack a lot of stuff in their soil, so if you add nutes on top of whats already in the soil, you're overfeeding. you have to let your plants use up whats already there before you add more. when you see growth slow down, and the very first signs of any deficiencies, like new growth coming in light colored, thats when you want to start using more nutes.
almost all nutes come in the form of mineral "salts", if you don't water till you see about 10% run off, those salts build up in the soil and slowly poison your plant. a good flush to start with will get rid of a lot of that, but i'd make sure i'm getting a little run through each time i water to avoid salt build up.