I use em. Sound like a freakin sales rep for fox farm over here, but like I said, it's what I've always used and I like the results. Take it slow at first. 1/4 strength from what their feeding schedule says, 1/2 strength, and up from there. Let your plants tell you how hungry they are. I have only used the 3 pack though (big bloom, grow big, & tiger bloom). Never tried the solubles...so couldn't tell ya about those. Only other additive I use is unsulphered blackstrap molasses during the last few weeks of flowering.... Good luck w the grow!