Both were developed for seed to flower. Each has a little different NPK ratio but pretty much the same.
This is the thing. I can plant a particular genetic in Happy Frog
and it'll blow up yet I put it in Fox Farm
and for some reason it just doesn't like it and gives you problems throughout. In the eyes of the gardener Happy Frog
is the bomb and Fox Farms sucks yet we know, through others experience, that Fox Farms most certainly DOESN'T suck but the gardener will post his experience and claim that his post is fact because that's what happened to him. So many factors other than soil could have made that happen but he blames it on the soil without really understanding what went wrong. This is why I take opinions on the internet with a grain of salt. Until I can verify that this person knows what they're talking about I'll listen but I won't take it as truth unless I can independently verify or I've experienced the same thing myself under the same conditions.
The enclosure you built is going to have a hard time keeping PPM up every time you open the door. 100lb tank is too much. A 25 lb aluminum tank should last you at least a month but it all depends on how tight your enclosure is. You don't want that shit leaking into your bedroom(I'm assuming that's where you built your box).
I'm not sure what to say about your experience because what you described is contrary to what should happen unless there is something you left out. A pound of dry ice isn't going to do what you described. Not sure what happened in that grow that induced that kind of growth but I think I can say that the dry ice wasn't what did it.
What are you planning on doing for air circulation in your box? How will you exhaust heat and humidity out of the box? These two questions are going to put a dent in your CO2 idea.