24-8-16 sounds like Miracle Grow All purpose. Use care, as it's real concentrated. I believe I was adding 1/2 teaspoon per gallon, once a week, (when I used to use it) but is not acceptable for flowering. You'll need a mellow bloom fert low in nitrogen. No additional nutes though, till the time release nutes wears-out of the soil.
When you order your ph pen, perhaps you could order some quality nutrients too. Usually best to stick with veg and bloom ferts from the same maker. Prevents imbalances and makes life easier.