Hello there
First off, for gnats, i would add premium wormcastig to fry them, or use nematodes, or you can use a botanical stinging nettle tea, garlic and cillantro also work. These are organics methods that cost next to nothing and can be sourced locally.
Everything u need to know to grow organic dank, and or use organic methods for pest control, is in here
https://www.rollitup.org/organics/636057-recycled-organic-living-soil-rols.html
And btw ur deffeciancy is because u are using bottle nutes that made from a petro based chemical. Also due to ur bag soil that probley doesnt have quality amendments. Mix those to factors and bam nuclear explosion..
However, ur plants look healthy on top! My advise (if it still matters)
Less is better, start trying out teas, and add top dressing, like wormcasting and or compost and kelp. I promise your plants will respond with joy!
good luck