Iron is considered a micronutrient.
Flourish (comprehensive) is a trace mix with small amounts of macronutrients.
Flourish Trace is just a trace mix.
If you are already dosing macronutrients via Seachem Nitrogen, Phosphorus and Potassium, then while Flourish (comprehensive) is fine, you could just use Flourish Trace (this could be important if one is cheaper than the other).
I think that iron being a micro nutrient, is a debatable topic.
Lol, I can't believe that this slipped all my research and knowledge of plants, I should just stick with flourish trace and skip the comp. I'll just increase the dosing by 1ml each or so, i'll do the calculations later. Thanks for showing me the obvious lol.