I've got some GH liquid Kool Bloom 0-10-10 here, but haven't used it. Any experience with that?
No, sorry. The only liquids I use are hydrolysed fish ferts, home made calmag, and RO water. Liquid feeds tend to bypass the soil biota and feed the plant directly, which crashes brix.
In the presence of adequate light and minerals, high brix only really requires 5 things. Calcium, Phosphorus, Carbon, Oxygen, and beneficial aerobic soil microbes/fungii.
Carbon comes from the air. O2 does too but overwatering displaces it from the rootball.
Calcium is activated by water, so dry calcium in the soil or a calmag solution will work, and P MUST come thru a microbe.
And then of course microbes and fungii.
The plant knows that in order to get the microbes/fungii to deliver the food it must bribe them, so it creates excess sugars to trade for food, and P is the hardest food to get, so you need more sugars for bribery.
If you bypass the microbes and give P straight to the plant, such as liquid P does, there is now far less need for sugars, and it all crashes.
So in a nutshell, you need adequate light and minerals to drive photosynthesis, and then you need a proper balnce of the big 5, Calcium, Carbon, Oxygen, Phosphorus, and microbes/fungii. That sets up the sugar factory.
So for most soil growers it's just an adjustment. For hydro growers it's a complete change.
LOS is meant to produce high brix, it's natures way, so if you are using LOS and brix are low it's almost always overwatering, which restricts oxygen, or low calcium.