My first hydro grow I used Botanicare Grow & Bloom. Out of 4 plants I only got like 60 grams total.
My second hydro grow I used Advanced Nutrients 2 part system with no additives. Out of 4 plants I got just under 100 grams.
My third hydro grow I used Advanced Nutrients and all the additives they recommend. Out of 4 plants I got close to 300 grams.
My fourth hydro grow I did the SOG method and used Advanced Nutrients with all the additives they recommend. Out of 8 plants I got close to 400 grams.
My fifth hydro grow I did the same method in the fourth grow and ended up with close to 500 grams with 8 plants. The only thing I did different was, I added CO2 to the flowering room.
I would have to say yes.....using additives does make a huge difference, especially if it's hydro.
Just a little extra info on my grows....
All of my grows were bloomed under a 400 watt HPS.
My point is. A plants food is not just the light, it's the nutrient.
There are 3 things that plants need.
The best Light........At least 55,000 lumens
The best Nutrient....A 2 part system with additives
The best Air...........A constant flow of fesh air, with 1500 PPM's of CO2
If you keep these 3 things in mind while your growing, your harvests will pay off.