you could, but I don't really like the 707 mix, personally.
The vermifire is a much better soil, as well as the fox farm. The vermifire is a great mix, my favorite when I used bagged soil yrs ago. And I used it for my base for my ROLS/no-till containers, I added a BUNCH of stuff to it, but it's an excellent base, with the volcanic rock in particular.
If you do use the 707, you could add probably 1/2-3/4 of a cup of nutrients to it safely (each bag), provided you add the right type of nute, in other words slow releasers, if you were to add 3/4 cup of blood meal, you'd be chapped.
but i'd 1/4 cup of each of the following
neem meal, kelp meal, and crab meal.
I'd also add a half cup of minerals too, basalt, azomite, etc.
I'd also add more castings/compost to that also.
A water only with the 707 is going to be a lil hard, it drains a lil too much, i'd add compost castings and those nutes I mentioned.
let it sit for a month ideally.