lights are everything.. you fertilizer is 5-10% and likely even less... more about not causing problems than anything else as far as our input in the process.
you feed relative to what the lights cuase in the plant...
in general, people boost "P" in bloom... but, i'm not a fan of a darstic chemical shift in fertilizer at anytime. (organic ferts are chemicals... can't avoid it. thoe molecules still has to adhere to reality liek any other molecules.)