Thrive Alive and FoxFarm Grow Big

Hey guys, first-time grower here. I have a 2x4x5 foot grow tent setup. I recently picked up a few clones and transplanted them into Roots Organics' original potting soil. The soil is supposed to contain enough nutrients for a week or so before I need to add more. They are in 3-gallon fabric smart pots. I went to my local GrowBiz store and the guy recommended I get both Thrive Alive B-1 Green seaweed-based tonic and a bottle of FoxFarm grow big for the vegetative stage. I was wondering opinions on these brands and how you guys would recommend using them. Any info and help would be appreciated, thanks!