I don't run
Athena but from the guys I know that do they don't drop core at week 5 and I believe core also has the micro's in it, so dropping it would be a mistake, Athene runs a particular ratio blend so if you start screwing with it to much your going to do more harm then good. I'd still follow their feed chart reasonably close and cut back on core week 7 and 8 as stated.
Athena runs heavy K and light on N Ca and Mg, I could possibly see adding a little Ca and Mg preferrably independently with the core as is in feed chart, but like I said I don't run
athena and I haven't personally tried that.
Also ignore what OjoRowJo said, lack of knowledge and ignorance usually leads to the dumbest post of the day