28 ppm of P is what your currently running with the amounts you provided...you posted you use 2 grams of P per gallon in your bloom formula
given only those elements you stated you use in your bloom mix you would need to raise the K drastilcy to get the P up
the addition of mpk or monopotassium phosphate makes a world of difference in how i would mix it... I didn't realize your where making that addition
I thought the question was how would I mix it using only the 3 elements you mentioned
2g Ca N
2g 5-12-26
1.5 grams mg-s
is what you said you where using