WeGroanswered grow question 3 years ago 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.)