as a new rule I stick to 3:1:2, as plants use 3 times more N then P etc
For this reason, I believe in decreasing N as opposed to adding PK during bloom, as plants can only use so much P & K,. Any more is wasted, and can cause toxicity issues.
a good product in soil is sulfate of potash. 50# bag at the local farm supply is less then $20. A few teaspoons in a 5 gal bucket with molasses and it doesn't get much better. 1 bag will last 10 years.