New grower here. I went with the
GH Flora series for my grow after doing a lot of reading. Might try
Advanced Nutrients for my next grow.
As far as when to use nutes you want to be using now for sure. I believe you want to be using 1/2 strength of recommended GH dosage, although I know some people use up to 80% of recommended dosage. It really depends on how your plants are feeding on it and how your PH balances out. You should also be checking PPM on your nutes to make sure they are in a good range.