I wondered about sheep pellets until I looked up your home page and noted your New Zealand address. If your citrus labeled fertilizer is complete with all the minors citrus requires, that is all I would use. Here in California, it is recommended that container citrus is fertilized monthly, about a tablespoon each application, scratched into the soil surface. This not a timed release type fertilizer. I have never seen a citrus fertilizer claimed to be timed release. Al

Yeah. No shortage sheep pellets available here! :)

The citrus granules contain most if what's needed and says 2 table spoons last for up to 3 months.

Does this make anymore sense?

Yes the directions sound pretty standard for the bags of citrus labeled fertilizer available here. They don't take into account the benefits of the fast draining mixes you are using. These citrus fertilizers do not use polymer coated granules that provide true time delay feeding based on soil temperatures. I stand by my monthly feeding recommendations, and use the sheep pellets on your in the ground plants. I will in the next day or two post the list of micro nutrients citrus needs for best performance.
My daughter and her husband spend every winter in NZ where they have come to love the people. Al

This is from a Lilly Miller Citrus Food label