I use N-P-K 5:15:14
(NOTE the 2nd number is the phosperous, much needed for BLOOMING) with added:
CALCIUM 5%, MAGNESIUM 3.5%,
SULPHUR 4%, IRON .1%,
AND BORON, COPPER, CHLORIDE,
MOLYBDENUM, AND ZINC .01%
You want the nutes where the 2nd number is the highest, for blooming. Use your 15-30-15,or 10-52-10 in small doses and they will work great.