It's likely the water availability. Yes plants can self regulate water uptake to a degree, but it's like me trying to regulate myself around chocolate cake. They aren't growing to taste good: they are growing to survive. Thus, taking up a fuck ton of water is in their best interest as a plant.
You are dead on balls. If you ever get any additional experience hydroponically growing.... Things... There's a ton of micronutrients and minerals that a plant needs to fuel taste and smell.
It's mostly figured out and you can get a series of minerals and micronutrients chelated into a salt. They dissolve without large particulates in the water to not foul a water pump. Those are either suspended in solution or sold dry. You can even check how much available nutrition there is to a plant by checking the ppm and electrical conductivity of the water.
Dead on about myco too, in soil or a soil mix, if you aren't feeding water with properly mixed nutrients, you need both raw amendments (crushed up plants/shells/rocks/guano/insect frass)and myco/bacteria to break everything down and make them available to the plant.
That's for things you are growing for consumption, much less complicated if you just want something to be green, or flower with pretty colors.
