It used to be a running joke to say “hydro shop guy says what?” Now there are some good ones out there but IME far and few between. As
@CannaGranny said they are there to sell. Just like car salesman.
From someone that has no benefit to lie to you, this is my suggestion. The more things you add the more likely you are to mess up your grow. Further to that i feel like you should keep it simple and establish a baseline so you know what that looks like. Otherwise you will not know what products are benefiting you and which are not.
There are so many magic snake oils in a bottle it will make your head spin. Many of them contain the same things in slightly different ratio and imho you will have the most success with a simple compete base nutrient.
Terps and flavonoids biggest impact is a proper dry and cure. No additive will do more than that.
What are you using right now?