Frankensteins Lab Leader
I too find 450 ppm to be a good on average. I have however found some want a bit more. Even then 550 seems to be good for those. I had some photos go yellow in early flower, a bump up to 550 fixed that and they were fine the rest of the grow. If you grow many different strains like I do, you just want to watch them close as the enter flowering.
As I approach 500 ppm (EC=1) in hydro, nute burn becomes more likely.
450 is my sweet spot.