One problem with using the fertilizers we use is the amount of potassium they contain. If you want to replicate say Miracle gro all purpose you either have to reduce the nitrogen considerably to match potassium or raise the potassium A LOT
. Better sources of nitrogen for terrestrial plants are the urea and ammonia based forms. That's one of the reasons you see them used on most terrestrial fertilizers.
Terrestrial plants have various requirements. A fertilizer good for trees is not good for flowers. As far as your maple, you may be better off re-potting it with soil rich in organics or using slow release fertilizers. Japanese maples are not heavy feeders. In fact, using liquids with high nitrogen can kill them quite quickly.
is a popular hydroponic solution. I have used that as a liquid fertilizer. You would need Ca(NO3)2 (calcium Nitrate) and MgSO4.7H2O (epsom salt).
Here is a close approximation using what you have plus the extra calcium and Magnesium.
This makes 1 gallon.
Ca(NO3)2.4H2O 4.461 gm (approximately 1/4 teaspoons)
KNO3 2.018 gm (approximately 1/2 teaspoons)
KH2PO4 515.58 mg (approximately 1/16 teaspoons)
MgSO4.7H2O 1.823 gm (approximately 1/4 teaspoons)
Plantex CSM+B 144.925 mg (approximately 1/32 teaspoons)