Use Epsom salts for the 'mag', your tap water will probably have enough 'cal' in it.
But if growing in soil, no need for 'cal-mag' it's a hydro supplement.
I just use cheap chemical fertiliser ......... $5/kg or less, works fine.
All that seems to matter is the NPK values 20-10-30 for veg (same as MC), then add 0-52-34 as well for flower.
I know I'll get slammed for this, but I always use household mosquito and insect spray.
Bit of a spritz in the tent, not on the leaves, fans off, tent zipped for an hour.
Don't wet the leaves ..... the plant will die.
(it's a gas not a wash)
Try best looking plant for no flush.
Using the worst looking plant will only confirm your prejudices.
Flushing is just not sensible, as is not feeding your plant when it's ripening.
Do farmers flush/starve their crops weeks before harvest?
Does your bread/apples/tobacco taste worse because they...
Been cloning everything the past month, (lockdown caused boredom) toppings, straws, lower growth, old growth, new growth. Everything has rooted, the straws and more woody older growth just takes a few days longer for the roots to show. 8-10 days and they have roots and ready to pot.
I just stick the cuttings in the top of my humidifier, and leave it on the windowsill.
10 days later it's ready to pot.
No bags, no scraping, no cutting at angles, no chemicals, no special hygiene.
Woody or soft or straw, it does't matter, they all grow roots ...... soft is a couple of days faster.