How quickly do plants react to under or over nutrients

Hi all, new to hydroponics, and growing in general really. I made a small hydro setup in a wardrobe. I was wondering, how long does it take on average for a plant to show signs of to many or to little nutrients? I was wondering because im finding it tricky to tell if im getting it right or not :/

Not tricky at all if you have the proper tools to start a new project. Cheap ppm pens can be found.