S and Mg will boost resin more a the end of flowering so good old Epsom Salts are good to add.
tbh I just found a mentioning to use Gypsum for this, which seems to be perfect as its Ca & S. Or maybe a combination? So Mg increases in need towards midflower as well? tbh I never ran about this, but Im just as of now digging a bit deeper into influencing nutrient ratios.
Some of these seem to be esp. important...
@Dr. Who do you by chance know more of those...?
I remember seeing a chart somewhere placing Potassium & Calcium @ 2:1, but thats been generally for plants not Cannabis specific.
Keeping these ratios in cheek may help preventing locks or should enable a better growthrate at higher ECs... esp. when mixing together different brands.
If we just could exemplify an ideal target full NPK formulae for each individual growthphase of Cannabis, then it would be easy to find the required products (starting with cheap powder not expensive bottles that are mostly water)....
e.g. "High Veg Formulae":
N 12, P 4, K 10, S 2, Ca 5, Mg 1.5, Fe 0.5, Mn + Micros ?
... just to illustrate an example.