Welcome to TPT Animag!
You're already way ahead of most people with only a few weeks experience. Realizing Leafzone only provides potash and iron is spot on.
I would certainly dose phosphates. Many new to the hobby have heard the myth that it causes algae. Trust me, it's a myth. In fact, to the contrary. Not supplying adequate phosphates will cause algae. So let me be the first to tell you to dismiss that myth.
The other fertilizers you listed are perfect. There are two groups of nutrients we want to supply, macros and micros. The macros are NPK usually listed as three numbers on most fertilizers for example, 30-0-10 for your lawn. Those are Nitrogen (nitrates for us), Potassium and Phosphorus (phosphates for us) respectively. The others are "everything else" which we get from Plantex CSM +B. Many people also purchase extra iron as a supplement. This is probably a good idea. I would look for DTPA iron, the percentage is not important.
Which method to use? This seems to cause a lot of confusion. It appears to most people that they have to choose a method. Instead, choose to simply supply your plants with non-limiting nutrients at all times. This is the concept of the EI method. The normal EI dose is for high tech tanks. However, it can be reduced and modified any way we like. As long as we maintain specific levels of nutrients to never limit plant growth. This eliminates nutrient deficiencies and a lot of guess work. Yes, it can also be used for 30% weekly water changes although 50% is a better target IMO.
As Korya said here is a thread, Dry dosing and nutrient solution recipes.
, listing doses for common tank sizes. I think it's important to first understand why we dose what we do. Here, EI concept explained
, is a link to a post I made explaining the EI "Concept". Notice the concept and not method? I feel this should be viewed as a target to achieve rather than blindly dosing a recommended amount, otherwise viewed as a method. Non-limiting nutrients is the ONLY way to maximize growth based on nutrients. So basically when choosing a "method" there aren't really any options. It's simple logic. Call the method anything you like. Providing non-limiting nutrients regarless of your parameters is the only way to fly IMO.