I'm gonna make this super simplified and basic as it is not anything to panic about or over-think.
Plants need 3 macro nutrients and lots of micro's. The Big 3 are N-P-K. Nitrogen, phosphorous and potassium. Nitrogen is for growing. Phosphorous and potassium is for roots and buds.
As much as we would love to just pour tons of nutes on her to get big, that will kill her.
If you feed to much/often, it also can/will affect taste/potency,etc.
Sometimes the soil has enough 'stuff' that all you need is water. This is basic idea of organic.
When she starts looking a little pale or weak, it may be because she is growing so fast she is using all her stored N. That's her telling you she is hungry.
As for the proper amount, that is medium and plant specific in my opinion. I now try to feed as little as possible and stay out of the girls way. Some plants want nutrients every watering. Some want 1/4 the recommended dose every 3rd watering. They are not all the same.
Here are some links that may help you figure out the basics of nutrients more clearly than i explained.
Macro Micro nutrients
WHAT DOES N-P-K mean?