I think changing weekly is bullsh!t, bigass waste.
Unless i have lockout or infection i go thru whole veg without swapping out nute soup...but i’m on it like flies on stink.
I do 2nd change at or 1 week after 12:12, switching over to flower nutes, next change after first pistil flush... unless there are probs...next one in late flower 3-4 days before flush, using pre-flush nutes (see technaflora recipe for success to find what the preflush nutes are), then i refill with pH’d water w hg/gff and go till harvest....
Works for me, has a lot to do with keeping everything on target, maybe my particular nutes, but i doubt it.
Btw, nutes are at the bottom of my list for growing strong and big yields....like a lot of farmers, i think nutes are nutes...no need to add pretty labeled, heavy hyped, pricey sh!t...your lights and dialed in process are what counts the most.
npk and micros are the same no matter what bag, bottle, compost pile they come from...