Simple, tried and true.......pH all ingoing fluids to 6.5....
Your using MG nuted soil,,,,,,sigh,,,,,,not the best choice! Be SURE not to overwater! Let your soil dry out pretty well before waterings. Over watering and keeping the soil on the "wet" side will release more of the "nutrients" in the soil..
Use some Ca/Mg now and then.
USE a liquid "zyme" product to keep the living things in the soil at good levels. Canna, Hesi, AN, and others make this......
Avoid Kelp products and Humic Acid supplements as they will increase nutrient uptake......You don't want that with MG soil!
Silica can be helpful with MG soils as it helps temper or regulate the "P" that is high in MG soil.....
DO NOT add any form of "bloom boosters" to MG soil runs.
Good Luck.