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Your plants are happy, you've given them plenty of space in the containers. You could continue using containers and do great. However plants in the ground will always yield more than plants in containers. Even if your native soil is clay and unproductive.
What I'd try is either scraping out a container-sized hole in the ground. Fill it with your good mix and let them rip. Once the roots take hold over a long season they'll inevitably get bigger and should yield more. This is a multi-year project. Year after year as you amend the soil it will change. Loosen and become easier to work as you use beneficial amendments.
There are drawbacks to direct planting. You won't be able to move your plants easily. This can be a problem in certain situations. Pests can be a bigger problem. Animals are more likely to chew on, dig around, and climb up plants direct in the soil than in containers. You might need some type of fencing, or at least protection around the base of the stalk. I haven't needed it but in a lot of places they're necessary.
Another option is to build a 'container' above ground. An old time Mendocino grower taught me this trick. Their soil is legendary for how hard and worthless it is. He'd take sticks and tar paper and construct a makeshift container on top of the soil. He'd staple and tie it together, about the size of one of your containers or even bigger. Fill it with good stuff. Even though it's above ground the plants can get their roots down deep.
There's a benefit to letting the plant get it's taproot in the ground and spread out. The biggest benefit isn't depth so much as width. Cannabis plants spread out over a wide area, 6 out or more. It's much bigger than you'd think. This is the biggest problem with containers, they aren't wide enough. Just giving the plant it's freedom to stretch will improve yield.
If you're 'size restricted'. Or at the max of the yield you need. Why mess with a good thing? Nothing wrong with continuing what you're doing. I've found growing huge plants is a lot of fun, trying to outdo yourself year after year. Changing your garden soil is an ongoing process. Over a few years you can change your soil from an unyielding hard clay to soft fluffy perfection. That's the beauty of growing in the same spot year after year.