Question about Fertilizer...

[Dimples]

I’d suspect another of the needed conditions for growth would be to blame for the ailing plants, not the fertilizer. The frequency of significant nutrient imbalances when you’re using a complete formula, or a nearly complete formula with occasional tap water for the Ca/Mg, is going to be very low.

If you don’t flush occasionally and delay repotting too long, then you could start to see issues as nutrients buildup in the pot and throw things off balance, but that’s avoidable. Same for equal value fertilizers like your 20-20-20. They start out imbalanced from the plant’s perspective from the start. They’re fine if you use them lightly, so your method is good. I prefer a true all-purpose/all-plant formula in a 3-1-2 ratio but I also grow tropicals and outdoor plants.