Most flower fertiliser have more potassium (potash) in their ratios, the same as Tomato fertiliser (av 14:10:27)
The ordinary Miracle gro all purpose has NPK of 15:13:12 so doesn't encourage flowers
On the labels the ratio is shown as NPK it's the last one that you need to be high, and a flower fertiliser will be probably be cheaper than a tomato one, but if tomato fert is what you have then use it
Too late for flowers IMO