I recommend using phosphate after repotting. Actually, the source of the phosphate doesn't matter much. It could be bones,
superphosphate, bat guano (Colombian or Jamaican) or something from a test tube.
IN general fertilization practice really depends on your soil construction and watering habits as much as what you are growing. Technical things like pH and CEC ratio may play into the equation.
1. I would hesitate to make any real specific recommendations as to what you should do, except to say "DON'T WASTE YOUR TIME WITH OLD GOLD JUNIPER UNLESS IT IS A 50 YEAR-OLD STUMP COLLECTED WITH A FORKLIFT, TWO MEN AND A BOY" But I am not so opinionated as to say anything like that.
2. I think Superthrive ( in and of itself) is overkill, read the packaging
3. Your fertilization regimen sounds aggressive, but I don't know what concentration you're talking about applying with every watering. I would suggest you try one or the other at the recommended concentration when used once a week and then adjust the frequency of fertilization from there (more or less),
4. Experiment with using different fertilization regimens. Hit one plant weekly and another every other week. Keep notes and don't change things more frequently than once every month or two, or you'll never know what caused what.
Regards,
Matt