Theres a ton of info, dosing methods, etc. However, I can suggest the simplest of them all: EI dosing.
In this dosing method, you add a set amount of dry ferts to your tank daily. The idea is to give your plants much more ferts than they could possibly use in a week, and then dilute them by change 50% or more of the water every week. The ferts you need for any type of dosing is as follows:
Macros: KNO3, KH2PO4
Optional: Chelated Iron, GH Booster
There is a great sticky here in the top of this forum that tells you how much to dose per day depending on your tank size. If its a bit too much for you, post your tank specs and we can help you with a schedule.
The other important factor is co2. You say youve had co2 set up for over a year, but what kind? You want your drop checker to be on the verge or yellow, or slightly yellow.