If you’re running hydro the idea is that you monitor and adjust EC to try to find the sweet spot whereby water and nutrients are uptaken at the same rate and EC stays stable.
however this “sweet spot” is constantly changing.
try this for starters and watch and adjust as necessary.
seedling/early Veg - 0.6
Mid veg - 0.8-1.0
Late veg - 1.0-1.2
Stretch 1.0-1.4
Mid flower - 1.0-1.4
Late flower - 0.6-1.0