Regarding nutrients, here is my take:
There are lots of companies that make cannabis nutes, and some of them are
sponsors here. There are powders, liquids, and ones you mix into your soil and then top dress every two weeks or so. Each one has their own philosophy on what combination of elements makes the best plants and harvests.
Let me start by getting a few things out of the way, and this information is what I have picked up both here and from research on the internet. Cannabis (indeed most plants) need
very little phosphorus, whether in veg or flower which is why most boosters are a waste of money.
This is a pdf with plant analysis charts and graphs (with full detailed lab analysis) done on the macro and micronutrients found in three different strains of cannabis plant during veg and flower.
The varieties and analysis are from 2003, but I don't think we have modified the plant in the last 17 years to the extent that the nutrient results would vary that greatly today. Here are screenshots of the first three graphs that show NPK, Ca, Mg, and S (sulfur).:
Besides showing how little phosphorus the plants are using compared to nitrogen and potassium, it shows the continued need for nitrogen in flower.
You can also see that though the need for K does go up in flower, so does nitrogen, blowing up another nute myth not to feed your plants nitrogen in flower.
The charts show you what your plants need through veg and flower, so that's what you should feed them. The next step is to find nutrients that are available to you and in your budget that allow you to do that.
