Right now, I am using 2 tsp per gallon, but I had to work up to that. Maybe start with 1.5 Tsps and make sure they handle that. Seeing the plants are so large.. they will probably handle more.... But start with 1.5, then move to two. I think the directions say between 2-3 tsps per gallon?? and your BIG plants will probably need that but start small so you don't accidentally burn them...
On mine, I started with 1 moved to 1.5 then to two.. That's all they can handle I can tell by looking at them.. At the same time though, mine are a lot smaller than yours.
Maybe Stinky will be able to help you as well and we can figure out what's probably best for your plants together..... I have never grown anything so large