WeGroanswered grow question 3y The leaf's will tell you. when the plant start to turn light green, uniformly, thats the signal that they are running out of nuets.
when your new, theres a learning curve and that is going to effect your grow (in a subtle way).
for next grow, if you use same soil/neuts-brands, you will be able to time the neut insertions better, so your plants dont even need to tell you :)
and then there wont be a small, almost insignificant growth stall, that occurse when plants needs to cannablize itself for neuts. (turning light green/towards yellow.)